County of Marin Health and Human Services

Influenza Activity Updates

Marin County Department of Health and Human Services tracks influenza activity by analyzing laboratory testing data and visits to local emergency departments for influenza-like illness. The influenza season runs from early October to late May, usually peaking between late December and early February.  During influenza season, we produce a weekly influenza surveillance report that summarizes influenza activity in Marin County, California, and the United States.

As expected each season, influenza activity has started to increase in the Bay Area. This week, there have been coordinated county press releases in the region about local influenza activity. The following is a partial Influenza Surveillance Update Report with up-to-date information about recent influenza trends in Marin County. A full Influenza Surveillance Update Report will be released on MarinFlu.org next week (during the week of January 9th).

Clinical Updates

Rapid Influenza Diagnostic Tests can be falsely negative when the prevalence of influenza is high, as it currently is in Marin County.  The California Department of Public Health advises that these tests should not be used for making treatment decisions in persons at higher risk for influenza complications.  Real-time PCR is the preferred laboratory testing method when influenza infection is suspected.  

Marin

Local influenza activity began increasing during the week of December 11th, with a substantial increase in positive influenza tests during the last week of December (December 25-31) (Figure 1). 

Influenza testing1 

During week 52 (December 25-31), 70 (34.8%) of the 201 specimens tested for influenza were positive.  Of the positive specimens from week 52, 69 (99%) were influenza A and 1 (1%) was influenza B. During this influenza season through December 31, 128 specimens have tested positive for influenza.  See Figure 1 below.

Figure 1.  Influenza Tests in Marin County, 2016-2017 Influenza Season
Influenza Tests in Marin County, 2014-2015

1Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, Novato Community Hospital, and Sutter Terra Linda Urgent Care.

Visit MarinFlu.org for influenza vaccination, testing, and treatment recommendations.

California

  • The geographic spread of influenza activity in California increased to widespreadduring week 51 (December 18-24), the most recent week for which data are available.
  • Of the specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories, 20.8% (808 of 3,886 specimens tested) were positive for influenza during week 51. Of these, 796 (98.5%) were positive for influenza A and 12 (1.5%) were positive for influenza B.  Of the influenza A specimens, 5 (0.6%) were subtyped as 2009 A (H1), 35 (4.4%) were subtyped as seasonal A (H3), and 756 (95.0%) were not subtyped.
  • Visit the California Department of Public Health’s influenza surveillance website for more information.  

United States

  • Influenza activity is rising nationally.
  • Of the specimens tested and reported by the U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories, 10.4% (1,813 of 17,395 specimens tested) were positive for influenza during week 51 (December 18-24), the most recent week for which data are available.  
  • For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

+Widespread: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in at least half the regions of the state with recent laboratory evidence of influenza in the state.

If you have any questions or comments please contact:
Haylea Hannah, MSPH
Epidemiology Fellow
(415) 473-6020
HHannah@marincounty.org

This publication is provided to you by the Office of the Public Health Officer, County of Marin Department of Health and Human Services.

Sources

California Department of Public Health. https://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%2051%20-%20FINAL%20Report.pdf. Accessed 1/5/2017.

Centers for Disease Control and Prevention. https://www.cdc.gov/flu/weekly/. Accessed 1/5/2017.

Influenza Surveillance Update Survey

Please take five minutes to respond to our Influenza Surveillance Update Survey: https://www.surveymonkey.com/r/59N9JDC.

Marin County Health and Human Services is conducting a short survey to determine how providers and other public health personnel use our Influenza Surveillance Update reports to inform their clinical practice. We are also soliciting suggestions for how to improve the surveillance updates. Your responses to the survey are anonymous and will only be analyzed in aggregate.

Marin

During the past month of this influenza season (April 17-May 14), influenza activity continued to decrease in Marin County, with a reduction in both influenza-like illness activity (Figure 1) and the percent of influenza tests testing positive (Figure 2). Due to the substantial reduction in both positive influenza tests and influenza-like illness, this report is the last of the 2015-2016 influenza season.

Influenza-like illness activity
Influenza-like illness activity in Marin County decreased during weeks 16-19 (April 17-May 14) in comparison to past weeks of this influenza season. Discharge data from Kaiser San Rafael, Marin General Hospital, and Novato Community Hospital emergency departments and visits to Sutter Terra Linda Urgent Care showed the percentage of visits associated with influenza-like illness (ILI) was 7.8% during week 19. See Figure 1 below.

Figure 1: Proportion of Visits due to Influenza-Like Illness (ILI): Kaiser San Rafael, MGH, and NCH Emergency Departments and Sutter Terra Linda Urgent Care, 2013-14, 2014-2015, and 2015-2016 Influenza Seasonsiliwks1415.jpg

PROVISIONAL DATA, SUBJECT TO CHANGE. The case definition for ILI is any chief complaint that includes the following keywords or variants of the keywords: influenza, flu, influenza-like illness, pneumonia, fever, cough, and/or sore throat.

Influenza testing1
There was a marked reduction in the number of influenza tests conducted and the number of positive influenza tests during weeks 16-19 (April 17-May 14). During week 19, 3 (11.5%) of the 26 specimens tested for influenza were positive. Of the positive specimens from week 19, 2 (66.7%) were influenza A and 1 (33.3%) was influenza B. During this influenza season through May 14, 222 specimens have tested positive for influenza. See Figure 2 below.

Figure 2. Influenza Tests in Marin County, 2015-2016 Influenza Seasonlabwks1415final.jpg

PROVISIONAL DATA, SUBJECT TO CHANGE.

1 Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, Novato Community Hospital, and Sutter Terra Linda Urgent Care.

Visit MarinFlu.org for influenza vaccination, testing, and treatment recommendations.

California

  • Influenza activity is within expected levels in California.
  • Outpatient ILI activity as a percentage of total visits to sentinel providers was within expected levels for this time of year during week 19 (1.7%).
  • Of the specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories during week 19, 6.9% (49 of 715 specimens tested) were positive for influenza. Of these, 26 (53.1%) were positive for influenza A and 23 (46.9%) were positive for influenza B. Of the influenza A specimens, 6 (23.1%) were subtyped as 2009 A (H1), 2 (7.7%) were subtyped as seasonal A (H3), and 18 (69.2%) were not subtyped.
  • The geographic spread of influenza activity in California was local^ during week 19.
  • Visit the California Department of Public Health's influenza surveillance website for more information.

United States

  • Influenza activity decreased nationally during week 19.
  • The proportion of outpatient visits for influenza-like illness (ILI) was 1.4% during week 19, below the national baseline of 2.1%.
  • Of the specimens tested and reported by the U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories, 7.1% (741 of 10,510 specimens tested) were positive for influenza during week 19.
  • During week 19, the geographic spread of influenza activity was reported as widespread+ in two states, regional* in seven states, local^ in 19 states and the District of Columbia, and sporadic~ in 22 states. See map below for week 19.
  • For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

usmap15.jpg

+Widespread: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in at least half the regions of the state with recent laboratory evidence of influenza in the state.
*Regional: Outbreaks of influenza or increases in ILI and recent laboratory confirmed influenza in at least two but less than half the regions of the state with recent laboratory evidence of influenza in those regions
^Local: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in a single region of the state.
~Sporadic: Small numbers of laboratory-confirmed influenza cases or a single laboratory-confirmed influenza outbreak has been reported, but there is no increase in cases of ILI.

Additional flu trends can be seen in Google Flu Trends which uses aggregated Google search data in a model created in collaboration with CDC to estimate influenza activity in the United States. For more information and activity estimates from California, the U.S. and worldwide, see http://www.google.org/flutrends/

If you have any questions or comments please contact:
Haylea Hannah, MSPH
Epidemiology Fellow
(415) 473-6020
HHannah@marincounty.org

This publication is provided to you by the Office of the Public Health Officer, County of Marin Department of Health and Human Services.

Sources

California Department of Public Health. http://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%2019%20-%20FINAL%20Report.pdf. Accessed 5/25/2016.

Centers for Disease Control and Prevention. https://www.cdc.gov/flu/weekly/. Accessed 5/25/2016.

Influenza Surveillance Update

Due to decreasing influenza activity in Marin County, we will be releasing our next and last influenza surveillance update report of the season in one month, during the last week of May. If you have any questions about influenza activity in the meantime, please reach out to Haylea Hannah at HHannah@marincounty.org or (415) 473-6020.

Marin

During weeks 14 (April 3-9) and 15 (April 10-16), influenza activity was decreasing in Marin County, with a reduction in both influenza-like illness activity (Figure 1) and the number of positive influenza tests (Figure 2).

Influenza-like illness activity
Influenza-like illness activity in Marin County decreased during weeks 14 (April 3-9) and 15 (April 10-16) in comparison to peak activity observed during this influenza season. Discharge data from Kaiser San Rafael, Marin General Hospital, and Novato Community Hospital emergency departments and visits to Sutter Terra Linda Urgent Care showed the percentage of visits associated with influenza-like illness (ILI) was 10.4% during week 14 and 8.9% week 15. See Figure 1 below.

Figure 1: Proportion of Visits due to Influenza-Like Illness (ILI): Kaiser San Rafael, MGH, and NCH Emergency Departments and Sutter Terra Linda Urgent Care, 2013-14, 2014-2015, and 2015-2016 Influenza Seasonsiliwks1415.jpg

PROVISIONAL DATA, SUBJECT TO CHANGE. The case definition for ILI is any chief complaint that includes the following keywords or variants of the keywords: influenza, flu, influenza-like illness, pneumonia, fever, cough, and/or sore throat.

Influenza testing1
There was a marked reduction in the number of tests conducted during weeks 14 and 15, corresponding to a decrease in influenza-like illness. During week 142, 10 (17.5%) of the 57 specimens tested for influenza were positive. Of the positive specimens from week 14, 5 (50.0%) were influenza A and 5 (50.0%) were influenza B. During week 15, 9 (16.4%) of the 55 specimens tested for influenza were positive. Of the positive specimens from week 15, 4 (44.4%) were influenza A and 5 (55.6%) were influenza B. During this influenza season through April 16, 210 specimens have tested positive for influenza. See Figure 2 below.

Figure 2. Influenza Tests in Marin County, 2015-2016 Influenza Seasonlabwks1415final.jpg

PROVISIONAL DATA, SUBJECT TO CHANGE.

1 Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, Novato Community Hospital, and Sutter Terra Linda Urgent Care.

2 All data have not been received for week 14. Data are preliminary and subject to change.

Visit MarinFlu.org for influenza vaccination, testing, and treatment recommendations.

California

  • Influenza activity is continuing to decrease in California, however, laboratory data indicate that influenza activity is still elevated in some regions.
  • Outpatient ILI activity as a percentage of total visits to sentinel providers was below expected levels for this time of year during weeks 14 (2.3%) and 15 (1.5%).
  • Of the specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories during week 14, 13.8% (362 of 2,617 specimens tested) were positive for influenza. Of these, 194 (53.6%) were positive for influenza A and 168 (46.4%) were positive for influenza B. Of the influenza A specimens, 28 (14.4%) were subtyped as 2009 A (H1), 6 (3.1%) were subtyped as seasonal A (H3), and 160 (82.5%) were not subtyped.
  • Of the specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories during week 15, 10.7% (227 of 2,113 specimens tested) were positive for influenza. Of these, 105 (46.3%) were positive for influenza A and 122 (53.7%) were positive for influenza B. Of the influenza A specimens, 16 (15.2%) were subtyped as 2009 A (H1), 6 (5.7%) were subtyped as seasonal A (H3), and 83 (79.0%) were not subtyped.
  • The geographic spread of influenza activity in California decreased to regional* during week 15.
  • Visit the California Department of Public Health's influenza surveillance website for more information.

United States

  • Influenza activity decreased nationally during week 15.
  • The proportion of outpatient visits for influenza-like illness (ILI) was 2.1% during week 14 and 2.1% during week 15, both at the national baseline of 2.1%.
  • Of the specimens tested and reported by the U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories, 14.0% (2,544 of 18,188 specimens tested) were positive for influenza during week 14 and 13.4% (2,258 of 16,840 specimens tested) were positive for influenza during week 15.
  • During week 14, the geographic spread of influenza activity was reported as widespread+ in 18 states, regional* in 19 states, local^ in ten states and the District of Columbia, and sporadic~ in three states. During week 15, the geographic spread of influenza activity was reported as widespread+ in 14 states, regional* in 19 states, local^ in 13 states and the District of Columbia, and sporadic~ in four states. See map below for week 15.
  • For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

usmap15.jpg

+Widespread: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in at least half the regions of the state with recent laboratory evidence of influenza in the state.
*Regional: Outbreaks of influenza or increases in ILI and recent laboratory confirmed influenza in at least two but less than half the regions of the state with recent laboratory evidence of influenza in those regions
^Local: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in a single region of the state.
~Sporadic: Small numbers of laboratory-confirmed influenza cases or a single laboratory-confirmed influenza outbreak has been reported, but there is no increase in cases of ILI.

Additional flu trends can be seen in Google Flu Trends which uses aggregated Google search data in a model created in collaboration with CDC to estimate influenza activity in the United States. For more information and activity estimates from California, the U.S. and worldwide, see http://www.google.org/flutrends/

If you have any questions or comments please contact:
Haylea Hannah, MSPH
Epidemiology Fellow
(415) 473-6020
HHannah@marincounty.org

This publication is provided to you by the Office of the Public Health Officer, County of Marin Department of Health and Human Services.

Sources

California Department of Public Health. http://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%2014%20-%20FINAL%20Report.pdf and http://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%2015%20-%20FINAL%20Report.pdf. Accessed 4/25/2016.

Centers for Disease Control and Prevention. https://www.cdc.gov/flu/weekly/. Accessed 4/25/2016.

Marin

During weeks 12 (March 20-26) and 13 (March 27-April 2), influenza was still circulating in Marin County. However, influenza activity is decreasing, with a reduction in both influenza-like illness activity (Figure 1) and the number of positive influenza tests (Figure 2) during weeks 12 and 13.

Influenza-like illness activity

Influenza-like illness activity in Marin County decreased during weeks 12 (March 20-26) and 13 (March 27-April 2) in comparison to previous weeks of this influenza season. Discharge data from Kaiser San Rafael, Marin General Hospital, and Novato Community Hospital emergency departments and visits to Sutter Terra Linda Urgent Care showed the percentage of visits associated with influenza-like illness (ILI) was 10.1% during week 12 and 9.8% week 13. See Figure 1 below.

Figure 1: Proportion of Visits due to Influenza-Like Illness (ILI): Kaiser San Rafael, MGH, and NCH Emergency Departments and Sutter Terra Linda Urgent Care, 2013-14, 2014-2015, and 2015-2016 Influenza SeasonsInfluenza-like illness, Marin County, 2012-2015

PROVISIONAL DATA, SUBJECT TO CHANGE. The case definition for ILI is any chief complaint that includes the following keywords or variants of the keywords: influenza, flu, influenza-like illness, pneumonia, fever, cough, and/or sore throat.

Influenza testing1

During week 12, 12 (14.5%) of the 83 specimens tested for influenza were positive. Of the positive specimens from week 12, 6 (50.0%) were influenza A and 6 (50.0%) were influenza B. During week 13, 14 (15.2%) of the 92 specimens tested for influenza were positive. Of the positive specimens from week 13, 8 (57.1%) were influenza A and 6 (42.9%) were influenza B. During this influenza season through April 2, 191 specimens have tested positive for influenza. See Figure 2 below.

Figure 2. Influenza Tests in Marin County, 2015-2016 Influenza Season

PROVISIONAL DATA, SUBJECT TO CHANGE.

1 Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, Novato Community Hospital, and Sutter Terra Linda Urgent Care.

Visit MarinFlu.org for influenza vaccination, testing, and treatment recommendations.

California

  • Laboratory data indicate that influenza activity in California is still elevated, but is decreasing.
  • Outpatient ILI activity as a percentage of total visits to sentinel providers was above expected levels for this time of year during weeks 12 (3.1%) and 13 (1.8%).
  • Of the specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories during week 12, 16.8% (600 of 3,577 specimens tested) were positive for influenza. Of these, 267 (44.5%) were positive for influenza A and 333 (55.5%) were positive for influenza B. Of the influenza A specimens, 31 (11.6%) were subtyped as 2009 A (H1), 12 (4.5%) were subtyped as seasonal A (H3), and 224 (83.9%) were not subtyped.
  • Of the specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories during week 13, 16.3% (470 of 2,884 specimens tested) were positive for influenza. Of these, 229 (48.7%) were positive for influenza A and 241 (51.3%) were positive for influenza B. Of the influenza A specimens, 37 (16.2%) were subtyped as 2009 A (H1), 23 (10.0%) were subtyped as seasonal A (H3), and 169 (73.8%) were not subtyped.
  • The geographic spread of influenza activity in California remained widespread+ during week 13.
  • Visit the California Department of Public Health's influenza surveillance website for more information.

United States

  • Influenza activity decreased slightly, but remained elevated nationally.
  • The proportion of outpatient visits for influenza-like illness (ILI) was 2.9% during week 12 and 2.4% during week 13, both above the national baseline of 2.1%.
  • Of the specimens tested and reported by the U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories, 18.3% (4,022 of 21,959 specimens tested) were positive for influenza during week 12 and 16.2% (3,383 of 20,921 specimens tested) were positive for influenza during week 13.
  • During week 12, the geographic spread of influenza activity was reported as widespread+ in 29 states, regional* in 18 states, local^ in two states and the District of Columbia, and sporadic~ in one state. During week 13, the geographic spread of influenza activity was reported as widespread+ in 25 states, regional* in 18 states, local^ in four states and the District of Columbia, and sporadic~ in three states. See map below for week 13.
  • For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

usmap07.jpg

+Widespread: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in at least half the regions of the state with recent laboratory evidence of influenza in the state.
*Regional: Outbreaks of influenza or increases in ILI and recent laboratory confirmed influenza in at least two but less than half the regions of the state with recent laboratory evidence of influenza in those regions
^Local: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in a single region of the state.
~Sporadic: Small numbers of laboratory-confirmed influenza cases or a single laboratory-confirmed influenza outbreak has been reported, but there is no increase in cases of ILI.

Additional flu trends can be seen in Google Flu Trends which uses aggregated Google search data in a model created in collaboration with CDC to estimate influenza activity in the United States. For more information and activity estimates from California, the U.S. and worldwide, see http://www.google.org/flutrends/

If you have any questions or comments please contact:
Haylea Hannah, MSPH
Epidemiology Fellow
(415) 473-6020
HHannah@marincounty.org

This publication is provided to you by the Office of the Public Health Officer, County of Marin Department of Health and Human Services.

Sources

California Department of Public Health. http://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%2012%20-%20FINAL%20Report.pdf and http://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%2013%20-%20FINAL%20Report.pdf. Accessed 4/12/2016.

Centers for Disease Control and Prevention. https://www.cdc.gov/flu/weekly/. Accessed 4/12/2016.

Marin

During weeks 10 (March 6-12) and 11 (March 13-19), influenza was still circulating in Marin County. Both influenza-like illness activity (Figure 1) and the number of positive influenza tests (Figure 2) were at levels similar to the past few weeks of this influenza season, excluding a one week decline in both measures during week 9.

Influenza-like illness activity

Influenza-like illness activity in Marin County remained elevated during weeks 10 (March 6-12) and 11 (March 13-19), and increased in comparison to week 9, however, remained similar to week 8 activity. Discharge data from Kaiser San Rafael, Marin General Hospital, and Novato Community Hospital emergency departments and visits to Sutter Terra Linda Urgent Care showed the percentage of visits associated with influenza-like illness (ILI) was 13.2% during week 10 and 13.4% week 11. See Figure 1 below.

Figure 1: Proportion of Visits due to Influenza-Like Illness (ILI): Kaiser San Rafael, MGH, and NCH Emergency Departments and Sutter Terra Linda Urgent Care, 2013-14, 2014-2015, and 2015-2016 Influenza SeasonsInfluenza-like illness, Marin County, 2012-2015

PROVISIONAL DATA, SUBJECT TO CHANGE. The case definition for ILI is any chief complaint that includes the following keywords or variants of the keywords: influenza, flu, influenza-like illness, pneumonia, fever, cough, and/or sore throat.

Influenza testing1

During week 10, 22 (22.0%) of the 100 specimens tested for influenza were positive. Of the positive specimens from week 10, 18 (81.8%) were influenza A and 4 (18.2%) were influenza B. During week 11, 21 (20.8%) of the 101 specimens tested for influenza were positive. Of the positive specimens from week 11, 16 (76.2%) were influenza A and 5 (23.8%) were influenza B. During this influenza season through March 19, 165 specimens have tested positive for influenza. See Figure 2 below.

Figure 2. Influenza Tests in Marin County, 2015-2016 Influenza Season

PROVISIONAL DATA, SUBJECT TO CHANGE.

1 Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, Novato Community Hospital, and Sutter Terra Linda Urgent Care.

Visit MarinFlu.org for influenza vaccination, testing, and treatment recommendations.

California

  • Outpatient ILI activity and laboratory data indicate that influenza activity in California is still elevated, but is beginning to decrease.
  • Outpatient ILI activity as a percentage of total visits to sentinel providers was above expected levels for this time of year during weeks 10 (3.4%) and 11 (3.3%).
  • Of the specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories during week 10, 25.8% (1,101 of 4,270 specimens tested) were positive for influenza. Of these, 533 (48.4%) were positive for influenza A and 568 (51.6%) were positive for influenza B. Of the influenza A specimens, 66 (12.4%) were subtyped as 2009 A (H1), 14 (2.6%) were subtyped as seasonal A (H3), and 453 (85.0%) were not subtyped.
  • Of the specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories during week 11, 21.1% (885 of 4,186 specimens tested) were positive for influenza. Of these, 398 (45.0%) were positive for influenza A and 487 (55.0%) were positive for influenza B. Of the influenza A specimens, 49 (12.3%) were subtyped as 2009 A (H1), 19 (4.8%) were subtyped as seasonal A (H3), and 330 (82.9%) were not subtyped.
  • The geographic spread of influenza activity in California remained widespread+ during week 11.
  • Visit the California Department of Public Health's influenza surveillance website for more information.

United States

  • Influenza activity decreased slightly, but remained elevated nationally.
  • The proportion of outpatient visits for influenza-like illness (ILI) was 3.7% during week 10 and 3.2% during week 11, both above the national baseline of 2.1%.
  • Of the specimens tested and reported by the U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories, 23.1% (5,968 of 25,855 specimens tested) were positive for influenza during week 10 and 20.1% (4,816 of 23,946 specimens tested) were positive for influenza during week 11.
  • During week 10, the geographic spread of influenza activity was reported as widespread+ in 40 states, regional* in 10 states, and local^ in the District of Columbia. During week 11, the geographic spread of influenza activity was reported as widespread+ in 39 states, regional* in 10 states, and local^ in one state and the District of Columbia. See map below for week 11.
  • For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

usmap07.jpg

+Widespread: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in at least half the regions of the state with recent laboratory evidence of influenza in the state.
*Regional: Outbreaks of influenza or increases in ILI and recent laboratory confirmed influenza in at least two but less than half the regions of the state with recent laboratory evidence of influenza in those regions
^Local: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in a single region of the state.
~Sporadic: Small numbers of laboratory-confirmed influenza cases or a single laboratory-confirmed influenza outbreak has been reported, but there is no increase in cases of ILI.

Additional flu trends can be seen in Google Flu Trends which uses aggregated Google search data in a model created in collaboration with CDC to estimate influenza activity in the United States. For more information and activity estimates from California, the U.S. and worldwide, see http://www.google.org/flutrends/

If you have any questions or comments please contact:
Haylea Hannah, MSPH
Epidemiology Fellow
(415) 473-6020
HHannah@marincounty.org

This publication is provided to you by the Office of the Public Health Officer, County of Marin Department of Health and Human Services.

Sources

California Department of Public Health. http://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%2010%20-%20FINAL%20Report.pdf and http://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%2011%20-%20FINAL%20Report.pdf. Accessed 3/29/2016.

Centers for Disease Control and Prevention. https://www.cdc.gov/flu/weekly/. Accessed 3/29/2016.

Marin

During weeks 8 (February 21-27) and 9 (February 28-March 5), influenza was still circulating in Marin County, however, there was a marked reduction in both influenza-like illness activity and the number of positive influenza tests during week 9 (Figure 2).

Influenza-like illness activity

Influenza-like illness activity in Marin County remained elevated during weeks 8 (February 21-27) and 9 (February 28-March 5), however, decreased in comparison to recent weeks. Discharge data from Kaiser San Rafael, Marin General Hospital, and Novato Community Hospital emergency departments and visits to Sutter Terra Linda Urgent Care showed the percentage of visits associated with influenza-like illness (ILI) was 13.6% during week 8 and 12.3% week 9. See Figure 1 below.

Figure 1: Proportion of Visits due to Influenza-Like Illness (ILI): Kaiser San Rafael, MGH, and NCH Emergency Departments and Sutter Terra Linda Urgent Care, 2013-14, 2014-2015, and 2015-2016 Influenza SeasonsInfluenza-like illness, Marin County, 2012-2015

PROVISIONAL DATA, SUBJECT TO CHANGE. The case definition for ILI is any chief complaint that includes the following keywords or variants of the keywords: influenza, flu, influenza-like illness, pneumonia, fever, cough, and/or sore throat.

Influenza testing1

During week 8, 20 (23.0%) of the 87 specimens tested for influenza were positive. Of the positive specimens from week 8, 10 (50.0%) were influenza A and 10 (50.0%) were influenza B. During week 9, 11 (12.8%) of the 86 specimens tested for influenza were positive. Of the positive specimens from week 9, 7 (63.6%) were influenza A and 4 (36.4%) were influenza B. During this influenza season through March 5, 122 specimens have tested positive for influenza. See Figure 2 below.

Figure 2. Influenza Tests in Marin County, 2015-2016 Influenza Season

PROVISIONAL DATA, SUBJECT TO CHANGE.

1 Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, Novato Community Hospital, and Sutter Terra Linda Urgent Care.

Visit MarinFlu.org for influenza vaccination, testing, and treatment recommendations.

California

  • The geographic spread of influenza activity in California remained widespread+ during week 9.
  • Outpatient ILI activity as a percentage of total visits to sentinel providers was above expected levels for this time of year during weeks 8 (3.8%) and 9 (3.8%).
  • Of the specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories during week 8, 29.4% (1,602 of 5,453 specimens tested) were positive for influenza. Of these, 730 (45.6%) were positive for influenza A and 872 (54.4%) were positive for influenza B. Of the influenza A specimens, 89 (12.2%) were subtyped as 2009 A (H1), 26 (3.6%) were subtyped as seasonal A (H3), and 615 (84.2%) were not subtyped.
  • Of the specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories during week 9, 29.3% (1,343 of 4,581 specimens tested) were positive for influenza. Of these, 635 (47.3%) were positive for influenza A and 708 (52.7%) were positive for influenza B. Of the influenza A specimens, 52 (8.2%) were subtyped as 2009 A (H1), 17 (2.7%) were subtyped as seasonal A (H3), and 566 (89.1%) were not subtyped.
  • Visit the California Department of Public Health's influenza surveillance website for more information.

United States

  • Influenza activity remained elevated nationally.
  • The proportion of outpatient visits for influenza-like illness (ILI) was 3.2% during week 8 and 3.5% during week 9, both above the national baseline of 2.1%.
  • Of the specimens tested and reported by the U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories, 17.6% (3,803 of 21,615 specimens tested) were positive for influenza during week 8 and 20.6% (4,918 of 23,910 specimens tested) were positive for influenza during week 9.
  • During week 8, the geographic spread of influenza activity was reported as widespread+ in 33 states, regional* in 14 states, local^ in one state and the District of Columbia, and sporadic~ in two states. During week 9, the geographic spread of influenza activity was reported as widespread+ in 37 states, regional* in 13 states, and local^ in the District of Columbia. See map below for week 9.
  • For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

usmap07.jpg

+Widespread: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in at least half the regions of the state with recent laboratory evidence of influenza in the state.
*Regional: Outbreaks of influenza or increases in ILI and recent laboratory confirmed influenza in at least two but less than half the regions of the state with recent laboratory evidence of influenza in those regions
^Local: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in a single region of the state.
~Sporadic: Small numbers of laboratory-confirmed influenza cases or a single laboratory-confirmed influenza outbreak has been reported, but there is no increase in cases of ILI.

Additional flu trends can be seen in Google Flu Trends which uses aggregated Google search data in a model created in collaboration with CDC to estimate influenza activity in the United States. For more information and activity estimates from California, the U.S. and worldwide, see http://www.google.org/flutrends/

If you have any questions or comments please contact:
Haylea Hannah, MSPH
Epidemiology Fellow
(415) 473-6020
HHannah@marincounty.org

This publication is provided to you by the Office of the Public Health Officer, County of Marin Department of Health and Human Services.

Sources

California Department of Public Health. http://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%2008%20-%20FINAL%20Report.pdf and http://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%2009%20-%20FINAL%20Report.pdf. Accessed 3/14/2016.

Centers for Disease Control and Prevention. https://www.cdc.gov/flu/weekly/. Accessed 3/14/2016.

Marin

During weeks 6 (February 7-13) and 7 (February 14-20), influenza activity increased in Marin County in comparison to recent weeks with elevated influenza-like illness activity (Figure 1) and an increase in the number of positive influenza tests (Figure 2).

Influenza-like illness activity

Influenza-like illness activity in Marin County was elevated during weeks 6 (February 7-13) and 7 (February 14-20). Discharge data from Kaiser San Rafael, Marin General Hospital, and Novato Community Hospital emergency departments and visits to Sutter Terra Linda Urgent Care showed the percentage of visits associated with influenza-like illness (ILI) was 14.3% during week 6 and 14.2% week 7. See Figure 1 below.

Figure 1: Proportion of Visits due to Influenza-Like Illness (ILI): Kaiser San Rafael, MGH, and NCH Emergency Departments and Sutter Terra Linda Urgent Care, 2013-14, 2014-2015, and 2015-2016 Influenza SeasonsInfluenza-like illness, Marin County, 2012-2015

PROVISIONAL DATA, SUBJECT TO CHANGE. The case definition for ILI is any chief complaint that includes the following keywords or variants of the keywords: influenza, flu, influenza-like illness, pneumonia, fever, cough, and/or sore throat.

Influenza testing1

During week 6, 13 (13.5%) of the 96 specimens tested for influenza were positive.2 Of the positive specimens from week 6, 2 (15.4%) were influenza A and 11 (84.6%) were influenza B. During week 7, 18 (20.2%) of the 89 specimens tested for influenza were positive. Of the positive specimens from week 7, 9 (50.0%) were influenza A and 9 (50.0%) were influenza B. During this influenza season through February 20, 91 specimens have tested positive for influenza. See Figure 2 below.

Figure 2. Influenza Tests in Marin County, 2015-2016 Influenza Seasonlab_wks67.jpg

1 Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, Novato Community Hospital, and Sutter Terra Linda Urgent Care.

2All data have not been received for week 6. Data are preliminary and subject to change.

Visit MarinFlu.org for influenza vaccination, testing, and treatment recommendations.

California

  • The geographic spread of influenza activity in California remained widespread+ during week 7.
  • Outpatient ILI activity as a percentage of total visits to sentinel providers was above expected levels for this time of year during weeks 6 (4.1%) and 7 (4.0%).
  • Of the specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories during week 6, 24.0% (1,248 of 5,200 specimens tested) were positive for influenza. Of these, 619 (49.6%) were positive for influenza A and 629 (50.4%) were positive for influenza B. Of the influenza A specimens, 40 (6.5%) were subtyped as 2009 A (H1), 14 (2.3%) were subtyped as seasonal A (H3), and 565 (91.3%) were not subtyped.
  • Of the specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories during week 7, 31.8% (1,596 of 5,015 specimens tested) were positive for influenza. Of these, 767 (48.1%) were positive for influenza A and 829 (51.9%) were positive for influenza B. Of the influenza A specimens, 75 (9.8%) were subtyped as 2009 A (H1), 23 (3.0%) were subtyped as seasonal A (H3), and 669 (87.2%) were not subtyped.
  • Visit the California Department of Public Health's influenza surveillance website for more information.

United States

  • Influenza activity increased from previous weeks.
  • The proportion of outpatient visits for influenza-like illness (ILI) was 3.1% during week 6 and 3.2% during week 7, both above the national baseline of 2.1%.
  • Of the specimens tested and reported by the U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories, 12.0% (2,135 of 17,797 specimens tested) were positive for influenza during week 6 and 13.8% (2,599 of 18,844 specimens tested) were positive for influenza during week 7.
  • During week 6, the geographic spread of influenza activity was reported as widespread+ in 12 states, regional* in 20 states, local^ in 15 states and the District of Columbia, and sporadic~ in three states. During week 7, the geographic spread of influenza activity was reported as widespread+ in 21 states, regional* in 18 states, local^ in 10 states and the District of Columbia, and sporadic~ in one state. See map below for week 7.
  • For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

usmap07.jpg

+Widespread: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in at least half the regions of the state with recent laboratory evidence of influenza in the state.
*Regional: Outbreaks of influenza or increases in ILI and recent laboratory confirmed influenza in at least two but less than half the regions of the state with recent laboratory evidence of influenza in those regions
^Local: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in a single region of the state.
~Sporadic: Small numbers of laboratory-confirmed influenza cases or a single laboratory-confirmed influenza outbreak has been reported, but there is no increase in cases of ILI.

Additional flu trends can be seen in Google Flu Trends which uses aggregated Google search data in a model created in collaboration with CDC to estimate influenza activity in the United States. For more information and activity estimates from California, the U.S. and worldwide, see http://www.google.org/flutrends/

If you have any questions or comments please contact:
Haylea Hannah, MSPH
Epidemiology Fellow
(415) 473-6020
HHannah@marincounty.org

This publication is provided to you by the Office of the Public Health Officer, County of Marin Department of Health and Human Services.

Sources

California Department of Public Health. http://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%2006%20-%20FINAL%20Report.pdf and http://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%2007%20-%20FINAL%20Report.pdf. Accessed 2/29/2016.

Centers for Disease Control and Prevention. https://www.cdc.gov/flu/weekly/. Accessed 2/29/2016.

Marin

During weeks 4 (January 24-30) and 5 (January 31-February 6), influenza was circulating in Marin County with elevated influenza-like illness activity (Figure 1). The number of positive influenza tests increased during week 5, leading to an increase in the percent positive (Figure 2).

Influenza-like illness activity

Influenza-like illness activity in Marin County was elevated during weeks 4 (January 24-30) and 5 (January 31-February 6). Discharge data from Kaiser San Rafael, Marin General Hospital, and Novato Community Hospital emergency departments and visits to Sutter Terra Linda Urgent Care showed the percentage of visits associated with influenza-like illness (ILI) was 12.9% during week 4 and 13.0% week 5. See Figure 1 below.

Figure 1: Proportion of Visits due to Influenza-Like Illness (ILI): Kaiser San Rafael, MGH, and NCH Emergency Departments and Sutter Terra Linda Urgent Care, 2013-14, 2014-2015, and 2015-2016 Influenza SeasonsInfluenza-like illness, Marin County, 2012-2015

PROVISIONAL DATA, SUBJECT TO CHANGE. The case definition for ILI is any chief complaint that includes the following keywords or variants of the keywords: influenza, flu, influenza-like illness, pneumonia, fever, cough, and/or sore throat.

Influenza testing1

During week 4, 7 (10.3%) of the 68 specimens tested for influenza were positive. Of the positive specimens from week 4, 5 (71.4%) were influenza A and 2 (28.6%) were influenza B. During week 5, 13 (13.5%) of the 96 specimens tested for influenza were positive. Of the positive specimens from week 5, 6 (46.2%) were influenza A and 7 (53.8%) were influenza B. During this influenza season through February 6, 60 specimens have tested positive for influenza. See Figure 2 below.

Figure 2. Influenza Tests in Marin County, 2015-2016 Influenza Season
Influenza Tests in Marin County, 2014-2015

1 Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, Novato Community Hospital, and Sutter Terra Linda Urgent Care.

Visit MarinFlu.org for influenza vaccination, testing, and treatment recommendations.

California

  • The geographic spread of influenza activity in California remained widespread+ during week 5.
  • Outpatient ILI activity as a percentage of total visits to sentinel providers was below expected levels for this time of year during weeks 4 (2.6%) and 5 (2.3%).
  • Of the specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories during week 4, 17.2% (536 of 3,120 specimens tested) were positive for influenza. Of these, 271 (50.6%) were positive for influenza A and 265 (49.4%) were positive for influenza B. Of the influenza A specimens, 11 (4.1%) were subtyped as 2009 A (H1), 5 (1.8%) were subtyped as seasonal A (H3), and 255 (94.1%) were not subtyped.
  • Of the specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories during week 5, 20.6% (864 of 4,189 specimens tested) were positive for influenza. Of these, 442 (51.2%) were positive for influenza A and 422 (48.8%) were positive for influenza B. Of the influenza A specimens, 38 (8.6%) were subtyped as 2009 A (H1), 12 (2.7%) were subtyped as seasonal A (H3), and 392 (88.7%) were not subtyped.
  • Visit the California Department of Public Health's influenza surveillance website for more information.

United States

  • Influenza activity increased slightly from previous weeks.
  • The proportion of outpatient visits for influenza-like illness (ILI) was 2.2% during week 4 and 2.4% during week 5, both above the national baseline of 2.1%.
  • Of the specimens tested and reported by the U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories, 6.8% (1,085 of 15,964 specimens tested) were positive for influenza during week 4 and 9.1% (1,563 of 17,175 specimens tested) were positive for influenza during week 5.
  • During week 4, the geographic spread of influenza activity was reported as widespread+ in three states, regional* in 18 states, local^ in 16 states and the District of Columbia, and sporadic~ in 12 states. No influenza activity was reported by one state. During week 5, the geographic spread of influenza activity was reported as widespread+ in seven states, regional* in 17 states, local^ in 16 states, and sporadic~ in nine states and the District of Columbia. No influenza activity was reported by one state. See map below for week 5.
  • For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

usmap03.jpg

+Widespread: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in at least half the regions of the state with recent laboratory evidence of influenza in the state.
*Regional: Outbreaks of influenza or increases in ILI and recent laboratory confirmed influenza in at least two but less than half the regions of the state with recent laboratory evidence of influenza in those regions
^Local: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in a single region of the state.
~Sporadic: Small numbers of laboratory-confirmed influenza cases or a single laboratory-confirmed influenza outbreak has been reported, but there is no increase in cases of ILI.

Additional flu trends can be seen in Google Flu Trends which uses aggregated Google search data in a model created in collaboration with CDC to estimate influenza activity in the United States. For more information and activity estimates from California, the U.S. and worldwide, see http://www.google.org/flutrends/

If you have any questions or comments please contact:
Haylea Hannah, MSPH
Epidemiology Fellow
(415) 473-6020
HHannah@marincounty.org

This publication is provided to you by the Office of the Public Health Officer, County of Marin Department of Health and Human Services.

Sources

California Department of Public Health. http://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%2004%20-%20FINAL%20Report.pdf and http://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%2005%20-%20FINAL%20Report.pdf. Accessed 2/16/2016.

Centers for Disease Control and Prevention. https://www.cdc.gov/flu/weekly/. Accessed 2/16/2016.

Severe Influenza Reported Nationally

The CDC released a health advisory urging rapid antiviral treatment of high risk suspect influenza patients without waiting for testing, as H1N1 viruses, which can cause more severe illness, have been more prominent in recent weeks. For more information about the predominant influenza strains observed at the state level during weeks 2 and 3, see the California section below. Currently, no cases of severe influenza have been reported in Marin.

Marin

During weeks 2 (January 10-16) and 3 (January 17-23), the number of positive influenza tests increased (Figure 2). Influenza-like illness increased during week 2 and decreased substantially during week 3, which is consistent with patterns observed at the state level during recent weeks.

Influenza-like illness activity

Influenza-like illness activity in Marin County was elevated during week 2 (January 10-16) and low during week 3 (January 17-23). Discharge data from Kaiser San Rafael, Marin General Hospital, and Novato Community Hospital emergency departments and visits to Sutter Terra Linda Urgent Care showed the percentage of visits associated with influenza-like illness (ILI) was 11.6% during week 2 and 7.3% week 31. See Figure 1 below.

Figure 1: Proportion of Visits due to Influenza-Like Illness (ILI): Kaiser San Rafael, MGH, and NCH Emergency Departments and Sutter Terra Linda Urgent Care, 2013-14, 2014-2015, and 2015-2016 Influenza SeasonsInfluenza-like illness, Marin County, 2012-2015

PROVISIONAL DATA, SUBJECT TO CHANGE. The case definition for ILI is any chief complaint that includes the following keywords or variants of the keywords: influenza, flu, influenza-like illness, pneumonia, fever, cough, and/or sore throat.

1All data have not been received for week 3. Data are preliminary and subject to change.

Influenza testing2

During week 2, 10 (15.4%) of the 65 specimens tested for influenza were positive. Of the positive specimens from week 2, 9 (90%) were influenza A and 1 (10%) was influenza B. During week 3, 6 (9.8%) of the 61 specimens tested for influenza were positive. Of the positive specimens from week 3, 3 (50%) were influenza A and 3 (50%) were influenza B. During this influenza season through January 23, 40 specimens have tested positive for influenza. See Figure 2 below.

Figure 2. Influenza Tests in Marin County, 2015-2016 Influenza Season
Influenza Tests in Marin County, 2014-2015

2 Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, Novato Community Hospital, and Sutter Terra Linda Urgent Care.

Visit MarinFlu.org for influenza vaccination, testing, and treatment recommendations.

California

  • The geographic spread of influenza activity in California increased to widespread+ during week 3.
  • Outpatient ILI activity as a percentage of total visits to sentinel providers was below expected levels for this time of year during weeks 2 (1.5%) and 3 (1.6%).
  • Of the specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories, 8.4% (414 of 4,952 specimens tested) were positive for influenza during week 2. Of these, 232 (56.0%) were positive for influenza A and 182 (44.0%) were positive for influenza B. Of the influenza A specimens, 14 (6.0%) were subtyped as 2009 A (H1), 14 (6.0%) were subtyped as seasonal A (H3), and 204 (87.9%) were not subtyped.
  • Of the specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories, 15.1% (453 of 2,992 specimens tested) were positive for influenza during week 3. Of these, 239 (52.8%) were positive for influenza A and 214 (47.2%) were positive for influenza B. Of the influenza A specimens, 25 (10.5%) were subtyped as 2009 A (H1), 14 (5.9%) were subtyped as seasonal A (H3), and 200 (83.6%) were not subtyped.
  • Visit the California Department of Public Health's influenza surveillance website for more information.

United States

  • Influenza activity increased slightly from previous weeks.
  • The proportion of outpatient visits for influenza-like illness (ILI) was 2.1% during week 2 and 2.2% during week 3.
  • Of the specimens tested and reported by the U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories, 4.2% (565 of 13,598 specimens tested) were positive for influenza during week 2 and 5.0% (680 of 13,517 specimens tested) were positive for influenza during week 3.
  • During week 2, the geographic spread of influenza activity was reported as widespread+ in three states, regional* in ten states, local^ in 12 states, and sporadic~ in 24 states. No influenza activity was reported in the District of Columbia and one state. During week 3, the geographic spread of influenza activity was reported as widespread+ in four states, regional* in 14 states, local^ in 12 states, and sporadic~ in 20 states and the District of Columbia. See map below for week 3.
  • For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

usmap03.jpg

+Widespread: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in at least half the regions of the state with recent laboratory evidence of influenza in the state.
*Regional: Outbreaks of influenza or increases in ILI and recent laboratory confirmed influenza in at least two but less than half the regions of the state with recent laboratory evidence of influenza in those regions
^Local: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in a single region of the state.
~Sporadic: Small numbers of laboratory-confirmed influenza cases or a single laboratory-confirmed influenza outbreak has been reported, but there is no increase in cases of ILI.

Additional flu trends can be seen in Google Flu Trends which uses aggregated Google search data in a model created in collaboration with CDC to estimate influenza activity in the United States. For more information and activity estimates from California, the U.S. and worldwide, see http://www.google.org/flutrends/

If you have any questions or comments please contact:
Haylea Hannah, MSPH
Epidemiology Fellow
(415) 473-6020
HHannah@marincounty.org

This publication is provided to you by the Office of the Public Health Officer, County of Marin Department of Health and Human Services.

Sources

California Department of Public Health. http://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%2002%20-%20FINAL%20Report.pdf and http://www.cdph.ca.gov/HealthInfo/discond/Documents/Influenza%20Weekly%20Report%20Week%20201603.pdf. Accessed 2/1/2016.

Centers for Disease Control and Prevention. https://www.cdc.gov/flu/weekly/. Accessed 2/1/2016.

Centers for Disease Control and Prevention. https://emergency.cdc.gov/han/han00387.asp. Accessed 2/3/2016.

Marin

During weeks 52 (December 27-January 2) and 1 (January 3-9), influenza-like illness remained low in Marin. The number of influenza tests conducted and the number of positive influenza tests have both increased in comparison to the past few weeks of the influenza season, leading to an increase in the percent positive (Figure 2).

Influenza-like illness activity

Influenza-like illness activity in Marin County was low during weeks 52 (December 27-January 2) and 1 (January 3-9). Discharge data from Kaiser San Rafael, Marin General Hospital, and Novato Community Hospital emergency departments and visits to Sutter Terra Linda Urgent Care showed the percentage of visits associated with influenza-like illness (ILI) remained at 10.1% during both week 52 and week 1. See Figure 1 below.

Figure 1: Proportion of Visits due to Influenza-Like Illness (ILI): Kaiser San Rafael, MGH, and NCH Emergency Departments and Sutter Terra Linda Urgent Care, 2013-14, 2014-2015, and 2015-2016 Influenza SeasonsInfluenza-like illness, Marin County, 2012-2015

PROVISIONAL DATA, SUBJECT TO CHANGE. The case definition for ILI is any chief complaint that includes the following keywords or variants of the keywords: influenza, flu, influenza-like illness, pneumonia, fever, cough, and/or sore throat.

Influenza testing1

During week 52, 4 (8.9%) of the 45 specimens tested for influenza were positive. All positive specimens from week 52 were influenza A. During week 1, 4 (6.3%) of the 63 specimens tested for influenza were positive. Of the positive specimens from week 1, 3 (75%) were influenza A and 1 (25%) was influenza B. During this influenza season through January 9, 24 specimens have tested positive for influenza. See Figure 2 below.

Figure 2. Influenza Tests in Marin County, 2015-2016 Influenza Season
Influenza Tests in Marin County, 2014-2015

1. Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, Novato Community Hospital, and Sutter Terra Linda Urgent Care.

Visit MarinFlu.org for influenza vaccination, testing, and treatment recommendations.

California

  • The geographic spread of influenza activity in California increased to regional*.
  • Outpatient ILI activity as a percentage of total visits to sentinel providers was above expected levels for this time of year during week 52 at 3.0% and below expected levels during week 1 at 1.3%.
  • Of the specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories, 5.4% (106 of 1,967 specimens tested) were positive for influenza during week 52 and 10.1% (354 of 3,518 specimens tested) were positive for influenza during week 1.
  • Visit the California Department of Public Health's influenza surveillance website for more information.

United States

  • Influenza activity increased slightly from previous weeks.
  • The proportion of outpatient visits for influenza-like illness (ILI) was 2.8% during week 52 and 2.0% during week 1.
  • Of the specimens tested and reported by the U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories, 1.8% (247 of 13,373 specimens tested) were positive for influenza during week 52 and 3.0% (428 of 14,269 specimens tested) were positive for influenza during week 1.
  • During week 52, the geographic spread of influenza activity was reported as widespread+ in two states, regional* in six states, local^ in 13 states, and sporadic~ in 27 states. No influenza activity was reported in the District of Columbia and two states. During week 1, the geographic spread of influenza activity was reported as regional* in nine states, local^ in 11 states, and sporadic~ in 28 states. No influenza activity was reported in the District of Columbia and two states. See map below for week 1.
  • For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

usmap01.jpg

+Widespread: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in at least half the regions of the state with recent laboratory evidence of influenza in the state.
*Regional: Outbreaks of influenza or increases in ILI and recent laboratory confirmed influenza in at least two but less than half the regions of the state with recent laboratory evidence of influenza in those regions
^Local: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in a single region of the state.
~Sporadic: Small numbers of laboratory-confirmed influenza cases or a single laboratory-confirmed influenza outbreak has been reported, but there is no increase in cases of ILI.

Additional flu trends can be seen in Google Flu Trends which uses aggregated Google search data in a model created in collaboration with CDC to estimate influenza activity in the United States. For more information and activity estimates from California, the U.S. and worldwide, see http://www.google.org/flutrends/

If you have any questions or comments please contact:
Haylea Hannah, MSPH
Epidemiology Fellow
(415) 473-6020
HHannah@marincounty.org

This publication is provided to you by the Office of the Public Health Officer, County of Marin Department of Health and Human Services.

Sources

California Department of Public Health. http://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%2052%20-%20FINAL%20Report.pdf and http://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%2001%20-%20FINAL%20Report.pdf. Accessed 1/19/2016.

Centers for Disease Control and Prevention. https://www.cdc.gov/flu/weekly/. Accessed 1/19/2016.

Marin

During weeks 50 (December 13-19) and 51 (December 20-26), influenza-like illness activity in Marin increased slightly from previous weeks (Figure 1). However, the percent of positive influenza tests decreased during weeks 50 and 51 in comparison to weeks 48 and 49 (Figure 2).

Influenza-like illness activity

Influenza-like illness activity in Marin County was low during weeks 50 (December 13-19) and 51 (December 20-26). Discharge data from Kaiser San Rafael, Marin General Hospital, and Novato Community Hospital emergency departments and visits to Sutter Terra Linda Urgent Care showed the percentage of visits associated with influenza-like illness (ILI) increased slightly to 9.2% during week 50 and 10.0% during week 51. See Figure 1 below.

Figure 1: Proportion of Visits due to Influenza-Like Illness (ILI): Kaiser San Rafael, MGH, and NCH Emergency Departments and Sutter Terra Linda Urgent Care, 2013-14, 2014-2015, and 2015-2016 Influenza SeasonsInfluenza-like illness, Marin County, 2012-2015

PROVISIONAL DATA, SUBJECT TO CHANGE. The case definition for ILI is any chief complaint that includes the following keywords or variants of the keywords: influenza, flu, influenza-like illness, pneumonia, fever, cough, and/or sore throat.

Influenza testing1

There were no positive tests during weeks 50 and 51 out of 29 and 27 tests conducted, respectively. During this influenza season through December 26, 16 specimens have tested positive for influenza. See Figure 2 below.

Figure 2. Influenza Tests in Marin County, 2015-2016 Influenza Season
Influenza Tests in Marin County, 2014-2015

1. Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, Novato Community Hospital, and Sutter Terra Linda Urgent Care.

Visit MarinFlu.org for influenza vaccination, testing, and treatment recommendations.

California

  • There has not been a report released on state-wide influenza activity for weeks 50 and 51.
  • Visit the California Department of Public Health's influenza surveillance website for more information on influenza activity during previous weeks.

United States

  • Influenza activity increased slightly during weeks 50 and 51 compared to previous weeks.
  • The proportion of outpatient visits for influenza-like illness (ILI) was 2.2% during week 50 and 2.6% during week 51, which are both above the national baseline of 2.1%.
  • Of the specimens tested and reported by the U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories, 2.9% (372 of 12,890 specimens tested) were positive for influenza during week 50 and 2.5% (282 of 11,448 specimens tested) were positive for influenza during week 51.
  • During week 50, the geographic spread of influenza activity was reported as regional* in five states, local^ in 14 states, and sporadic~ in 27 states and the District of Columbia. No activity was reported in four states. During week 51, the geographic spread of influenza activity was reported as widespread+ in one state, regional* in five states, local^ in 12 states, and sporadic~ in 29 states. No influenza activity was reported by three states and the District of Columbia. See map below for week 51.
  • For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

usmap49.jpg

+Widespread: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in at least half the regions of the state with recent laboratory evidence of influenza in the state.
*Regional: Outbreaks of influenza or increases in ILI and recent laboratory confirmed influenza in at least two but less than half the regions of the state with recent laboratory evidence of influenza in those regions
^Local: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in a single region of the state.
~Sporadic: Small numbers of laboratory-confirmed influenza cases or a single laboratory-confirmed influenza outbreak has been reported, but there is no increase in cases of ILI.

Additional flu trends can be seen in Google Flu Trends which uses aggregated Google search data in a model created in collaboration with CDC to estimate influenza activity in the United States. For more information and activity estimates from California, the U.S. and worldwide, see http://www.google.org/flutrends/

If you have any questions or comments please contact:
Haylea Hannah, MSPH
Epidemiology Fellow
(415) 473-6020
HHannah@marincounty.org

This publication is provided to you by the Office of the Public Health Officer, County of Marin Department of Health and Human Services.

Sources

Centers for Disease Control and Prevention. https://www.cdc.gov/flu/weekly/. Accessed 1/5/2016.

Marin

During week 48 (November 29-December 5) and week 49 (December 6-12), influenza-like illness remained minimal in Marin. The number of tests conducted has remained elevated since early November, however, there are still relatively few positive tests. The percent positive has not increased from prior weeks, which should serve as a reminder to all providers that it is not too late to discuss and offer immunization to our unvaccinated patient population.

Influenza-like illness activity

Influenza-like illness activity in Marin County was minimal during weeks 48 (November 29-December 5) and 49 (December 6-12). Discharge data from Kaiser San Rafael, Marin General Hospital, and Novato Community Hospital emergency departments and visits to Sutter Terra Linda Urgent Care showed the percentage of visits associated with influenza-like illness (ILI) increased slightly to 9.1% during week 48 and 8.8% during week 49. See Figure 1 below.

Figure 1: Proportion of Visits due to Influenza-Like Illness (ILI): Kaiser San Rafael, MGH, and NCH Emergency Departments and Sutter Terra Linda Urgent Care, 2013-14, 2014-2015, and 2015-2016 Influenza SeasonsInfluenza-like illness, Marin County, 2012-2015

PROVISIONAL DATA, SUBJECT TO CHANGE. The case definition for ILI is any chief complaint that includes the following keywords or variants of the keywords: influenza, flu, influenza-like illness, pneumonia, fever, cough, and/or sore throat.

Influenza testing1

During week 48, 1 (3.4%) of the 29 specimens tested for influenza was positive.2 The positive specimen from week 48 was influenza B. During week 49, 2 (5.4%) of the 37 specimens tested for influenza were positive. All positive specimens from week 49 were influenza A. During this influenza season through December 12, 16 specimens have tested positive for influenza. See Figure 2 below.

Figure 2. Influenza Tests in Marin County, 2015-2016 Influenza Season
Influenza Tests in Marin County, 2014-2015

1. Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, Novato Community Hospital, and Sutter Terra Linda Urgent Care.

2. All data have not been received for week 48. Data are preliminary and subject to change.

Visit MarinFlu.org for influenza vaccination, testing, and treatment recommendations.

California

  • Influenza activity in California remains minimal and sporadically~ distributed.
  • Outpatient ILI activity as a percentage of total visits to sentinel providers remained the same for weeks 48 and 49 at 1.9%.
  • Of the specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories, 2.5% (50 of 2,014 specimens tested) were positive for influenza during week 48 and 1.7% (23 of 1,344 specimens tested) were positive for influenza during week 49.
  • Visit the California Department of Public Health's influenza surveillance website for more information.

United States

  • Influenza activity increased slightly from previous weeks but remained low overall.
  • The proportion of outpatient visits for influenza-like illness (ILI) was 1.8% during week 48 and 1.9% during week 49.
  • Of the specimens tested and reported by the U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories, 1.6% (185 of 11,509 specimens tested) were positive for influenza during week 48 and 1.7% (208 of 12,525 specimens tested) were positive for influenza during week 49.
  • During week 48, the geographic spread of influenza activity was reported as local^ in 10 states and sporadic~ in 37 states. No activity was reported in the District of Columbia and three states. During week 49, the geographic spread of influenza activity was reported as regional* in two states, local^ in 12 states, and sporadic~ in the District of Columbia and 33 states. See map below for week 49.
  • For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

usmap49.jpg

+Widespread: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in at least half the regions of the state with recent laboratory evidence of influenza in the state.
*Regional: Outbreaks of influenza or increases in ILI and recent laboratory confirmed influenza in at least two but less than half the regions of the state with recent laboratory evidence of influenza in those regions
^Local: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in a single region of the state.
~Sporadic: Small numbers of laboratory-confirmed influenza cases or a single laboratory-confirmed influenza outbreak has been reported, but there is no increase in cases of ILI.

Additional flu trends can be seen in Google Flu Trends which uses aggregated Google search data in a model created in collaboration with CDC to estimate influenza activity in the United States. For more information and activity estimates from California, the U.S. and worldwide, see http://www.google.org/flutrends/

If you have any questions or comments please contact:
Haylea Hannah, MSPH
Epidemiology Fellow
(415) 473-6020
HHannah@marincounty.org

This publication is provided to you by the Office of the Public Health Officer, County of Marin Department of Health and Human Services.

Sources

California Department of Public Health. http://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%2049%20-%20FINAL%20Report.pdf and http://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%2048%20-%20FINAL%20Report.pdf. Accessed 12/18/2015.

Centers for Disease Control and Prevention. https://www.cdc.gov/flu/weekly/. Accessed 12/18/2015.

This is the first influenza surveillance report for the 2015-2016 influenza season.

Marin

During the first eight weeks of the 2015-2016 influenza season (October 4-November 28, 2015), influenza activity in Marin remained minimal and within expected levels for early in the season. We observed one outbreak in a skilled nursing facility, which contributed to the increase in positive influenza tests in week 44 (Figure 2, week starting date November 1).

Influenza-like illness activity:

Influenza-like illness activity in Marin County was minimal during week 47 (November 22 - 28, 2015). Discharge data from Kaiser San Rafael, Marin General Hospital, and Novato Community Hospital emergency departments and visits to Sutter Terra Linda Urgent Care showed the percentage of visits associated with influenza-like illness (ILI) was 8.58% during week 47. See Figure 1 below.

Figure 1: Proportion of Visits due to Influenza-Like Illness (ILI): Kaiser San Rafael, MGH, and NCH Emergency Departments and Sutter Terra Linda Urgent Care, 2013-2014, 2014-2015, and 2015-2016 Influenza Seasonsili_wks4647final.jpg

PROVISIONAL DATA, SUBJECT TO CHANGE. The case definition for ILI is any chief complaint that includes the following keywords or variants of the keywords: influenza, flu, influenza-like illness, pneumonia, fever, cough, and/or sore throat.

Influenza testing1: During week 47, 2 (5.9%) of the 34 specimens tested for influenza were positive. There was one positive influenza A specimen and one positive influenza B specimen. During this influenza season through November 28, 13 specimens have tested positive for influenza. See Figure 2 below.

Figure 2. Influenza Tests in Marin County, 2015-2016 Influenza Season
Influenza Tests in Marin County, 2015-2016

1. Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, Novato Community Hospital, and Sutter Terra Linda Urgent Care.

Visit MarinFlu.org for influenza vaccination, testing, and treatment recommendations.

California

  • During week 47, the geographic distribution of influenza activity in California was sporadic~.
  • Outpatient ILI activity as a percentage of total visits to sentinel providers was 1.0% in week 47.
  • Of the 1,298 specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories during week 47, 15 (1.2%) were positive for influenza; of these, 4 (26.7%) were positive for influenza B and 11 (73.3%) were positive for influenza A. Of the influenza A specimens, 5 (45.5%) were subtyped as seasonal A (H3) and 6 (54.5%) were not subtyped.
  • Kaiser Permanente hospitalization data for northern and southern California showed that the percentage of hospitalizations for flu admissions, defined as a diagnosis of "flu," "influenza," or "pneumonia" recorded in text fields at time of admission, was 4.9% during week 47.
  • No specimens from California residents have been strain-typed this season.
  • California Department of Public Health has received two reports of influenza-associated deaths in persons under age 65 during the 2015-2016 influenza season to date. None of these fatalities were reported in week 47.
  • The California Department of Public Health's Influenza website contains guidance and additional data.

United States

  • December 6-12, 2015 is National Influenza Vaccination Week (NIVW), which aims to promote the importance of continuing influenza vaccination. For more information, visit the Center for Disease Control and Prevention's NIVW website.
  • Influenza activity in the United States increased slightly, but remained low overall in week 47.
  • Of the 11,288 specimens tested and reported by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories during week 47, 171 (1.5%) were positive for influenza.
  • The proportion of deaths due to pneumonia and influenza (P&I) was below the epidemic threshold.
  • No influenza-associated pediatric deaths were reported during week 47.
  • The proportion of outpatient visits for influenza-like illness (ILI) was 1.9% during week 47.
  • Three of 10 regions reported a proportion of outpatient visits for ILI at or above the region-specific baseline level during week 47. ILI activity was moderate in two states, low in four states, and minimal in New York City and 44 states during week 47.
  • During week 47, the geographic spread of influenza activity was reported as local^ in seven states and sporadic~ in 38 states and the District of Columbia. Five states reported no influenza activity. See map below.
  • For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

Geographic Distribution of Influenza in the US

+Widespread: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in at least half the regions of the state with recent laboratory evidence of influenza in the state.
*Regional: Outbreaks of influenza or increases in ILI and recent laboratory confirmed influenza in at least two but less than half the regions of the state with recent laboratory evidence of influenza in those regions
^Local: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in a single region of the state.
~Sporadic: Small numbers of laboratory-confirmed influenza cases or a single laboratory-confirmed influenza outbreak has been reported, but there is no increase in cases of ILI.

Additional flu trends can be seen in Google Flu Trends which uses aggregated Google search data in a model created in collaboration with CDC to estimate influenza activity in the United States. For more information and activity estimates from California, the U.S. and worldwide, see http://www.google.org/flutrends/

If you have any questions or comments please contact:
Haylea Hannah, MSPH
Epidemiology Fellow
(415) 473-6020
HHannah@marincounty.org

This publication is provided to you by the Office of the Public Health Officer, County of Marin Department of Health and Human Services.

Sources

California Department of Public Health. http://www.cdph.ca.gov/HealthInfo/discond/Documents/2015%2011%2028%20Influenza%20Report.pdf. Accessed 12/07/2015.

Centers for Disease Control and Prevention. https://www.cdc.gov/flu/weekly/. Accessed 12/07/2015.

Marin

During week 10 (March 8-14) and week 11 (March 15-21), influenza-like illness activity in Marin County was below peak levels, but remained elevated compared to baseline levels (Figure 1). The number and percent of positive influenza tests continued decreasing, with only two positive tests reported in week 11 (Figure 2). Due to the substantial reduction in positive influenza tests and anticipated decline in influenza-like illness, this report is the last of the 2014-2015 influenza season.

Influenza-like illness activity

Influenza-like illness (ILI) in Marin County was moderate during week 10 (March 8-14) and week 11 (March 15-21). Discharge data from Kaiser San Rafael, Marin General Hospital, and Novato Community Hospital emergency departments and visits to Sutter Terra Linda Urgent Care showed the percentage of visits associated with ILI was 12.8% during week 10 and 13.1% during week 11. See Figure 1 below.

Figure 1. Proportion of Visits due to Influenza-Like Illness (ILI): Kaiser San Rafael, MGH, and NCH Emergency Departments and Sutter Terra Linda Urgent Care, 2012-13, 2013-14, and 2014-15 Influenza SeasonsInfluenza-like illness, Marin County, 2012-2015

PROVISIONAL DATA, SUBJECT TO CHANGE. The case definition for ILI is any chief complaint field that includes the following keywords or variants of the keywords: influenza, flu, influenza-like illness, pneumonia, fever, cough, and/or sore throat.

We updated the influenza-like illness (ILI) syndrome definition by broadening the list of chief complaints. As a result, the weekly percentages of visits for ILI are higher throughout the year than was seen using the prior definition, but the same general patterns from previous seasons remain. We applied the improved definition to all seasons in the graph above.

Influenza testing

During week 10, 6 (3.6%) of the 166 specimens tested for influenza were positive. During week 11, 2 (1.3%) of the 152 specimens tested for influenza were positive. Half of the positive specimens during week 10 were influenza A and the remaining specimens were influenza B. All positive specimens during week 11 were influenza A. As of March 21, 248 positive tests have been reported for the 2014-2015 influenza season. See Figure 2 below.

Figure 2. Influenza Tests in Marin County Reported by: Kaiser Novato, Kaiser San Rafael, Marin General Hospital, Novato Community Hospital, and Sutter Terra Linda Urgent Care, 2014-15 Influenza Season
Influenza Tests in Marin County, 2014-2015

Visit MarinFlu.org for influenza vaccination, testing, and treatment recommendations.

California

  • Overall influenza activity in California was regional* in week 10 and local^ in week 11.
  • Outpatient ILI activity as a percentage of total visits to sentinel providers was 3.1% in week 10 and 2.2% in week 11.
  • Of the 2,785 specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories during week 10, 264 (9.5%) were positive for influenza; of these, 93 (35.2%) were positive for influenza B and 171 (64.8%) were positive for influenza A. Of the influenza A specimens, 46 (26.9%) were subtyped as seasonal A (H3), none were subtyped as 2009 A (H1), and 125 (73.1%) were not subtyped. Of the 2,324 specimens tested during week 11, 160 (6.9%) were positive for influenza; of these, 67 (41.9%) were positive for influenza B and 93 (58.1%) were positive for influenza A. Of the influenza A specimens, 19 (20.4%) were subtyped as seasonal A (H3), none were subtyped as 2009 A (H1), and 74 (79.6%) were not subtyped.
  • Kaiser Permanente hospitalization data for northern and southern California showed that the percentage of hospitalizations for flu admissions, defined as a diagnosis of "flu," "influenza," or "pneumonia" recorded in text fields at time of admission, was 6.6% during week 10 and 5.9% during week 11.
  • California Department of Public Health has received 50 reports of influenza-associated deaths in persons under age 65 during the 2014-2015 influenza season to date.
  • The California Department of Public Health's Influenza website contains guidance and additional data.

United States

  • Influenza activity in the United States continued to decrease, but remained elevated in weeks 10 and 11.
  • Some circulating H3N2 strains differ from the H3N2 component of this season's influenza vaccine. The vaccine is still recommended. CDC released additional guidance on antiviral treatment.
  • Of the 15,033 specimens tested and reported by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories during week 10, 1,685 (11.2%) were positive for influenza. During week 11, 1,358 (10.6%) tests were positive for influenza of 12,824 tests conducted.
  • The proportion of deaths due to pneumonia and influenza (P&I) was above the epidemic threshold in weeks 10 and 11.
  • During week 10, three influenza-associated pediatric deaths were reported. During week 11, nine influenza-associated pediatric deaths were reported.
  • The proportion of outpatient visits for influenza-like illness (ILI) was 2.3% during week 10 and 2.2% during week 11.
  • During week 10, eight regions reported a proportion of outpatient visits for ILI at or above the region-specific baseline level. ILI activity was high in four states, moderate in six states, low in six states, and minimal in New York City and 34 states. During week 11, six regions reported a proportion of outpatient visits for ILI at or above the region-specific baseline level. ILI activity was high in one state, moderate in four states, low in 12 states, and minimal in New York City and 33 states.
  • During week 10, the geographic spread of influenza activity was reported as widespread+ in seven states, regional* in 29 states, local^ in 13 states, and sporadic~ in one state. During week 11, the geographic spread of influenza activity was reported as widespread+ in seven states, regional* in 27 states, local^ in 15 states, and sporadic~ in one state. See map below for week 11.
  • For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

Geographic Distribution of Influenza in the US

+Widespread: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in at least half the regions of the state with recent laboratory evidence of influenza in the state.
*Regional: Outbreaks of influenza or increases in ILI and recent laboratory confirmed influenza in at least two but less than half the regions of the state with recent laboratory evidence of influenza in those regions
^Local: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in a single region of the state.
~Sporadic: Small numbers of laboratory-confirmed influenza cases or a single laboratory-confirmed influenza outbreak has been reported, but there is no increase in cases of ILI.

Additional flu trends can be seen in Google Flu Trends which uses aggregated Google search data in a model created in collaboration with CDC to estimate influenza activity in the United States. For more information and activity estimates from California, the U.S. and worldwide, see http://www.google.org/flutrends/

If you have any questions or comments please contact:
Jessica Cunningham-Krahl, MPH
Epidemiologist
(415) 473-7346
JCunningham@marincounty.org

This publication is provided to you by the Office of the Public Health Officer, County of Marin Department of Health and Human Services.

Sources

Centers for Disease Control and Prevention. https://www.cdc.gov/flu/weekly/ and https://www.cdc.gov/flu/weekly/weeklyarchives2014-2015/week10.htm. Accessed 3/31/2015.

California Department of Public Health. http://www.cdph.ca.gov/data/statistics/Pages/CISPDataArchive.aspx. Accessed 3/31/2015.

Marin

During week 8 (February 22-28) and week 9 (March 1-7), influenza-like illness activity in Marin County decreased but remained elevated compared to baseline levels (Figure 1). A decline in the number and percent of positive influenza tests began in early February (Figure 2).

Influenza-like illness activity

Influenza-like illness (ILI) in Marin County was moderate during week 8 (February 22-28) and week 9 (March 1-7). Discharge data from Kaiser San Rafael, Marin General Hospital, and Novato Community Hospital emergency departments and visits to Sutter Terra Linda Urgent Care showed the percentage of visits associated with ILI was 11.9% during week 8 and 12.5% during week 9. See Figure 1 below.

Figure 1. Proportion of Visits due to Influenza-Like Illness (ILI): Kaiser San Rafael, MGH, and NCH Emergency Departments and Sutter Terra Linda Urgent Care, 2012-13, 2013-14, and 2014-15 Influenza SeasonsInfluenza-like illness, Marin County, 2012-2015

PROVISIONAL DATA, SUBJECT TO CHANGE. The case definition for ILI is any chief complaint field that includes the following keywords or variants of the keywords: influenza, flu, influenza-like illness, pneumonia, fever, cough, and/or sore throat.

We updated the influenza-like illness (ILI) syndrome definition by broadening the list of chief complaints. As a result, the weekly percentages of visits for ILI are higher throughout the year than was seen using the prior definition, but the same general patterns from previous seasons remain. We applied the improved definition to all seasons in the graph above.

Influenza testing

During week 8, 14 (7.9%) of the 177 specimens tested for influenza were positive. During week 9, 10 (5.8%) of the 173 specimens tested for influenza were positive. The majority of specimens during weeks 8 and 9 were influenza A (92.9% and 80.0%, respectively) and the remaining specimens were influenza B. As of March 7, 240 positive tests have been reported for the 2014-2015 influenza season. See Figure 2 below.

Figure 2. Influenza Tests in Marin County Reported by: Kaiser Novato, Kaiser San Rafael, Marin General Hospital, Novato Community Hospital, and Sutter Terra Linda Urgent Care, 2014-15 Influenza Season
Influenza Tests in Marin County, 2014-2015

Visit MarinFlu.org for influenza vaccination, testing, and treatment recommendations.

California

  • Overall influenza activity in California was widespread+ in week 8 and regional* in week 9.
  • Outpatient ILI activity as a percentage of total visits to sentinel providers was 3.1% in week 8 and 2.4% in week 9.
  • Of the 3,493 specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories during week eight, 396 (11.3%) were positive for influenza; of these, 65 (16.4%) were positive for influenza B and 331 (83.6%) were positive for influenza A. Of the influenza A specimens, 113 (34.1%) were subtyped as seasonal A (H3), 2 (0.6%) were subtyped as 2009 A (H1), and 216 (65.3%) were not subtyped. Of the 2,761 specimens tested during week nine, 307 (11.1%) were positive for influenza; of these, 65 (21.2%) were positive for influenza B and 242 (78.8%) were positive for influenza A. Of the influenza A specimens, 105 (43.4%) were subtyped as seasonal A (H3), none were subtyped as 2009 A (H1), and 137 (56.6%) were not subtyped.
  • Kaiser Permanente hospitalization data for northern and southern California showed that the percentage of hospitalizations for flu admissions, defined as a diagnosis of "flu," "influenza," or "pneumonia" recorded in text fields at time of admission, was 7.7% during week 8 and 7.2% during week 9.
  • California Department of Public Health has received 45 reports of influenza-associated deaths in persons under age 65 during the 2014-2015 influenza season to date.
  • The California Department of Public Health's Influenza website contains guidance and additional data.

United States

  • Influenza activity in the United States decreased, but remained elevated in week 8 and week 9.
  • Some circulating H3N2 strains differ from the H3N2 component of this season's influenza vaccine. The vaccine is still recommended. CDC released additional guidance on antiviral treatment.
  • Of the 16,821 specimens tested and reported by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories during week eight, 1,834 (10.9%) were positive for influenza. During week nine, 1,670 (11.4%) tests were positive for influenza of 14,634 tests conducted.
  • The proportion of deaths due to pneumonia and influenza (P&I) was at or above the epidemic threshold in weeks 8 and 9.
  • During week 8, six influenza-associated pediatric deaths were reported. During week 9, seven influenza-associated pediatric deaths were reported.
  • The proportion of outpatient visits for influenza-like illness (ILI) was 2.5% during week 8 and 2.4% during week 9.
  • During week 8, seven regions reported a proportion of outpatient visits for ILI at or above the region-specific baseline level. ILI activity was high in six states, moderate in four states, low in ten states, and minimal in New York City and 30 states. During week 9, eight regions reported a proportion of outpatient visits for ILI at or above the region-specific baseline level. ILI activity was high in six states, moderate in one state, low in 13 states, and minimal in New York City and 30 states.
  • During week 8, the geographic spread of influenza activity was reported as widespread+ in 12 states, regional* in 30 states, local^ in six states, and sporadic~ in two states. During week 9, the geographic spread of influenza activity was reported as widespread+ in nine states, regional* in 29 states, local^ in 11 states, and sporadic~ in one state. See map below for week 9.
  • For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

Geographic Distribution of Influenza in the US

+Widespread: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in at least half the regions of the state with recent laboratory evidence of influenza in the state.
*Regional: Outbreaks of influenza or increases in ILI and recent laboratory confirmed influenza in at least two but less than half the regions of the state with recent laboratory evidence of influenza in those regions
^Local: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in a single region of the state.
~Sporadic: Small numbers of laboratory-confirmed influenza cases or a single laboratory-confirmed influenza outbreak has been reported, but there is no increase in cases of ILI.

Additional flu trends can be seen in Google Flu Trends which uses aggregated Google search data in a model created in collaboration with CDC to estimate influenza activity in the United States. For more information and activity estimates from California, the U.S. and worldwide, see http://www.google.org/flutrends/

If you have any questions or comments please contact:
Jessica Cunningham-Krahl, MPH
Epidemiologist
(415) 473-7346
JCunningham@marincounty.org

This publication is provided to you by the Office of the Public Health Officer, County of Marin Department of Health and Human Services.

Sources

Centers for Disease Control and Prevention. https://www.cdc.gov/flu/weekly/ and https://www.cdc.gov/flu/weekly/weeklyarchives2014-2015/week8.htm. Accessed 3/18/2015.

California Department of Public Health. http://www.cdph.ca.gov/data/statistics/Pages/CISPDataArchive.aspx. Accessed 3/18/2015.

Marin

During week 6 (February 8-14) and week 7 (February 15-21), influenza-like illness activity in Marin County remained elevated (Figure 1). Compared to weeks 4 and 5, the number of positive tests decreased during weeks 6 and 7 while the total tests conducted remained high, leading to a reduction in the percent positive (Figure 2).

Influenza-like illness activity

Influenza-like illness (ILI) in Marin County was moderate during week 6 (February 8-14) and week 7 (February 15-21). Discharge data from Kaiser San Rafael, Marin General Hospital, and Novato Community Hospital emergency departments and visits to Sutter Terra Linda Urgent Care showed the percentage of visits associated with ILI was 14.5% during week 6 and 15.1% during week 7. See Figure 1 below. Because of the elevated levels of ILI, emergency rooms are experiencing surges in case loads and primary care providers are encouraged to assess and treat ILI symptoms when possible.

Figure 1. Proportion of Visits due to Influenza-Like Illness (ILI): Kaiser San Rafael, MGH, and NCH Emergency Departments and Sutter Terra Linda Urgent Care, 2012-13, 2013-14, and 2014-15 Influenza SeasonsInfluenza-like illness, Marin County, 2012-2015

PROVISIONAL DATA, SUBJECT TO CHANGE. The case definition for ILI is any chief complaint field that includes the following keywords or variants of the keywords: influenza, flu, influenza-like illness, pneumonia, fever, cough, and/or sore throat.

We updated the influenza-like illness (ILI) syndrome definition by broadening the list of chief complaints. As a result, the weekly percentages of visits for ILI are higher throughout the year than was seen using the prior definition, but the same general patterns from previous seasons remain. We applied the improved definition to all seasons in the graph above.

Influenza testing

During week 6, 22 (10.3%) of the 214 specimens tested for influenza were positive. During week 7, 17 (9.4%) of the 180 specimens tested for influenza were positive. The majority of specimens during week 6 and week 7 were influenza A (95.5% and 82.4%, respectively) and the remaining specimens were influenza B. As of February 21, 216 positive tests have been reported for the 2014-2015 influenza season. See Figure 2 below.

Figure 2. Influenza Tests in Marin County Reported by: Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, Novato Community Hospital, and Sutter Terra Linda Urgent Care, 2014-15 Influenza Season
Influenza Tests in Marin County, 2014-2015

Visit MarinFlu.org for influenza vaccination, testing, and treatment recommendations.

California

  • Overall influenza activity in California was widespread+ in weeks 6 and 7.
  • Outpatient ILI activity as a percentage of total visits to sentinel providers was 3.9% in week 6 and 3.7% in week 7.
  • Of the 4,611 specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories during week six, 791 (17.2%) were positive for influenza; of these, 79 (10.0%) were positive for influenza B and 712 (90.0%) were positive for influenza A. Of the influenza A specimens, 132 (18.5%) were subtyped as seasonal A (H3), none were subtyped as 2009 A (H1), and 580 (81.5 %) were not subtyped. Of the 3,736 specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories during week seven, 541 (14.5%) were positive for influenza; of these, 70 (12.9%) were positive for influenza B and 471 (87.1%) were positive for influenza A. Of the influenza A specimens, 134 (28.5%) were subtyped as seasonal A (H3), none were subtyped as 2009 A (H1), and 337 (71.5%) were not subtyped.
  • Kaiser Permanente hospitalization data for northern and southern California showed that the percentage of hospitalizations for flu admissions, defined as a diagnosis of "flu," "influenza," or "pneumonia" recorded in text fields at time of admission, was 8.0% during week 6 and 7.9% during week 7.
  • California Department of Public Health has received 38 reports of influenza-associated deaths in persons under age 65 during the 2014-2015 influenza season to date.
  • The California Department of Public Health's Influenza website contains guidance and additional data.

United States

  • Influenza activity in the United States decreased, but remained elevated in week 6 and week 7.
  • Some circulating H3N2 strains differ from the H3N2 component of this season's influenza vaccine. The vaccine is still recommended. CDC released additional guidance on antiviral treatment.
  • Of the 18,370 specimens tested and reported by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories during week six, 2,381 (13.0%) were positive for influenza. During week seven, 2,236 (12.1%) tests were positive for influenza of 18,505 tests conducted.
  • The proportion of deaths due to pneumonia and influenza (P&I) was above the epidemic threshold in weeks 6 and 7.
  • During weeks 6 and 7, six influenza-associated pediatric deaths were reported in each week.
  • The proportion of outpatient visits for influenza-like illness (ILI) was 3.2% during week 6 and 3.0% during week 7.
  • All 10 regions reported a proportion of outpatient visits for ILI at or above the region-specific baseline level during weeks 6 and 7. During week 6, ILI activity was high in 12 states, moderate in five states, low in New York City and 12 states, and minimal in 21 states. During week 7, ILI activity was high in 11 states, moderate in three states, low in 16 states, and minimal in New York City and 20 states.
  • During week 6, the geographic spread of influenza activity was reported as widespread+ in 30 states, regional* in 15 states, and local^ in five states. During week 7, the geographic spread of influenza activity was reported as widespread+ in 20 states, regional* in 25 states, and local^ in five states. See map below for week 7.
  • For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

Geographic Distribution of Influenza in the US

+Widespread: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in at least half the regions of the state with recent laboratory evidence of influenza in the state.
*Regional: Outbreaks of influenza or increases in ILI and recent laboratory confirmed influenza in at least two but less than half the regions of the state with recent laboratory evidence of influenza in those regions
^Local: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in a single region of the state.
~Sporadic: Small numbers of laboratory-confirmed influenza cases or a single laboratory-confirmed influenza outbreak has been reported, but there is no increase in cases of ILI.

Additional flu trends can be seen in Google Flu Trends which uses aggregated Google search data in a model created in collaboration with CDC to estimate influenza activity in the United States. For more information and activity estimates from California, the U.S. and worldwide, see http://www.google.org/flutrends/

If you have any questions or comments please contact:
Jessica Cunningham-Krahl, MPH
Epidemiologist
(415) 473-7346
JCunningham@marincounty.org

This publication is provided to you by the Office of the Public Health Officer, County of Marin Department of Health and Human Services.

Sources

Centers for Disease Control and Prevention. https://www.cdc.gov/flu/weekly/ and https://www.cdc.gov/flu/weekly/weeklyarchives2014-2015/week6.htm. Accessed 3/3/2015.

California Department of Public Health. http://www.cdph.ca.gov/data/statistics/Pages/CISPDataArchive.aspx. Accessed 3/3/2015.

Marin

During week 4 (January 25-31) and week 5 (February 1-7), influenza was circulating in Marin County with influenza-like illness activity remaining elevated (Figure 1). Compared to week 3, the number of positive tests increased slightly during weeks 4 and 5 while the total tests conducted increased substantially, leading to a reduction in the percent positive (Figure 2).

Influenza-like illness activity

Influenza-like illness (ILI) in Marin County was moderate during week 4 (January 25-31) and week 5 (February 1-7). Discharge data from Kaiser San Rafael, Marin General Hospital, and Novato Community Hospital emergency departments and visits to Sutter Terra Linda Urgent Care showed the percentage of visits associated with ILI was 16.6% during week 4 and 17.1% during week 5. See Figure 1 below. Because of the elevated levels of ILI, emergency rooms are experiencing surges in case loads and primary care providers are encouraged to assess and treat ILI symptoms when possible.

Figure 1. Proportion of Visits due to Influenza-Like Illness (ILI): Kaiser San Rafael, MGH, and NCH Emergency Departments and Sutter Terra Linda Urgent Care, 2012-13, 2013-14, and 2014-15 Influenza SeasonsInfluenza-like illness, Marin County, 2012-2015

PROVISIONAL DATA, SUBJECT TO CHANGE. The case definition for ILI is any chief complaint field that includes the following keywords or variants of the keywords: influenza, flu, influenza-like illness, pneumonia, fever, cough, and/or sore throat.

We updated the influenza-like illness (ILI) syndrome definition by broadening the list of chief complaints. As a result, the weekly percentages of visits for ILI are higher throughout the year than was seen using the prior definition, but the same general patterns from previous seasons remain. We applied the improved definition to all seasons in the graph above.

Influenza testing

During week 4, 34 (18.8%) of the 181 specimens tested for influenza were positive. During week 5, 36 (21.4%) of the 168 specimens tested for influenza were positive. The majority of specimens during week 4 and week 5 were influenza A (88.2% and 94.4%, respectively) and the remaining specimens were influenza B. As of February 7, 177 positive tests have been reported for the 2014-2015 influenza season. See Figure 2 below.

Figure 2. Influenza Tests in Marin County Reported by: Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, Novato Community Hospital, and Sutter Terra Linda Urgent Care, 2014-15 Influenza Season
Influenza Tests in Marin County, 2014-2015

Visit MarinFlu.org for influenza vaccination, testing, and treatment recommendations.

California

  • The geographic distribution of influenza activity in California was widespread+ in weeks 4 and 5.
  • Outpatient ILI activity as a percentage of total visits to sentinel providers was 5.2% in week 4 and 4.7% in week 5.
  • Of the 4,800 specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories during week four, 1,322 (27.5%) were positive for influenza; of these, 59 (4.5%) were positive for influenza B and 1,263 (95.5%) were positive for influenza A. Of the influenza A specimens, 267 (21.1%) were subtyped as seasonal A (H3), 1 (0.1%) was subtyped as 2009 A (H1) and 995 (78.8 %) were not subtyped. Of the 5,533 specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories during week five,1,429 (25.8%) were positive for influenza; of these, 90 (6.3%) were positive for influenza B and 1,339 (93.7%) were positive for influenza A. Of the influenza A specimens, 340 (25.4%) were subtyped as seasonal A (H3), 2 (0.1%) were subtyped as 2009 A (H1), and 997 (74.5%) were not subtyped.
  • Kaiser Permanente hospitalization data for northern and southern California showed that the percentage of hospitalizations for flu admissions, defined as a diagnosis of "flu," "influenza," or "pneumonia" recorded in text fields at time of admission, was 8.2% during week 4 and 8.3% during week 5.
  • California Department of Public Health has received 25 reports of influenza-associated deaths in persons under age 65 during the 2014-2015 influenza season to date.
  • The California Department of Public Health's Influenza website contains guidance and additional data.

United States

  • Influenza activity in the United States decreased, but remained elevated in week 4 and week 5.
  • Some circulating H3N2 strains differ from the H3N2 component of this season's influenza vaccine. The vaccine is still recommended. CDC released additional guidance on antiviral treatment.
  • Of the 22,122 specimens tested and reported by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories during week four, 3,869 (17.5%) were positive for influenza. During week five, 3,174 (14.9%) tests were positive for influenza of 21,340 tests conducted.
  • The proportion of deaths due to pneumonia and influenza (P&I) was above the epidemic threshold in weeks 4 and 5.
  • Eight influenza-associated pediatric deaths were reported during week 4. Eleven influenza-associated pediatric deaths were reported during week 5.
  • The proportion of outpatient visits for influenza-like illness (ILI) was 4.1% during week 4 and 3.8% during week 5.
  • All 10 regions reported a proportion of outpatient visits for ILI at or above the region-specific baseline level during weeks 4 and 5. During week 4, ILI activity was high in 26 states, moderate in New York City and eight states, low in six states, and minimal in 10 states. During week 5, ILI activity was high in 15 states, moderate in New York City and 15 states, low in eight states, and minimal in 12 states.
  • During week 4, the geographic spread of influenza activity was reported as widespread+ in 44 states, regional* in five states, and local^ in one state. During week 5, the geographic spread of influenza activity was reported as widespread+ in 32 states, regional* in 16 states, and local^ in two states. See map below for week 5.
  • For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

Geographic Distribution of Influenza in the US

+Widespread: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in at least half the regions of the state with recent laboratory evidence of influenza in the state.
*Regional: Outbreaks of influenza or increases in ILI and recent laboratory confirmed influenza in at least two but less than half the regions of the state with recent laboratory evidence of influenza in those regions
^Local: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in a single region of the state.
~Sporadic: Small numbers of laboratory-confirmed influenza cases or a single laboratory-confirmed influenza outbreak has been reported, but there is no increase in cases of ILI.

Additional flu trends can be seen in Google Flu Trends which uses aggregated Google search data in a model created in collaboration with CDC to estimate influenza activity in the United States. For more information and activity estimates from California, the U.S. and worldwide, see http://www.google.org/flutrends/

If you have any questions or comments please contact:
Jasmine Carver, MPH
Epidemiology Fellow
(415) 473-2573
JCarver@marincounty.org

This publication is provided to you by the Office of the Public Health Officer, County of Marin Department of Health and Human Services.

Sources

Centers for Disease Control and Prevention. https://www.cdc.gov/flu/weekly/ and http://www.cdc.gov/flu/weekly/weeklyarchives2014-2015/week4.htm . Accessed 2/17/2015.

California Department of Public Health. http://www.cdph.ca.gov/data/statistics/Pages/CISPDataArchive.aspx. Accessed 2/17/2015.

Marin

During week 2 (January 11-17) and week 3 (January 18-24), influenza was circulating in Marin County with influenza-like illness activity remaining elevated (Figure 1). Total influenza tests decreased slightly from week 1, however the number and proportion of specimens testing positive increased in week 3 (Figure 2).

Influenza-like illness activity

Influenza-like illness (ILI) in Marin County was moderate during week 2 (January 11-17) and week 3 (January 18-24). Discharge data from Kaiser San Rafael, Marin General Hospital, and Novato Community Hospital emergency departments and visits to Sutter Terra Linda Urgent Care showed the percentage of visits associated with ILI was 15.4% during week 2 and 14.8% during week 3. See Figure 1 below. Because of the elevated levels of ILI, emergency rooms are experiencing surges in case loads and primary care providers are encouraged to assess and treat ILI symptoms when possible.

Figure 1. Proportion of Visits due to Influenza-Like Illness (ILI): Kaiser San Rafael, MGH, and NCH Emergency Departments and Sutter Terra Linda Urgent Care, 2012-13, 2013-14, and 2014-15 Influenza SeasonsInfluenza-like illness, Marin County, 2012-2015

PROVISIONAL DATA, SUBJECT TO CHANGE. The case definition for ILI is any chief complaint field that includes the following keywords or variants of the keywords: influenza, flu, influenza-like illness, pneumonia, fever, cough, and/or sore throat.

We updated the influenza-like illness (ILI) syndrome definition by broadening the list of chief complaints. As a result, the weekly percentages of visits for ILI are higher throughout the year than was seen using the prior definition, but the same general patterns from previous seasons remain. We applied the improved definition to all seasons in the graph above.

Influenza testing

During week 2, 19 (18.4%) of the 103 specimens tested for influenza were positive. During week 3, 30 (27.8%) of the 108 specimens tested for influenza were positive. The majority of specimens during week 2 and week 3 were influenza A (94.7% and 83.3%, respectively) and the remaining specimens were influenza B. As of January 24, 107 positive tests have been reported for the 2014-2015 influenza season. See Figure 2 below.

Figure 2. Influenza Tests in Marin County Reported by: Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, Novato Community Hospital, and Sutter Terra Linda Urgent Care, 2014-15 Influenza Season
Influenza Tests in Marin County, 2014-2015

Visit MarinFlu.org for influenza vaccination, testing, and treatment recommendations.

California

  • The geographic distribution of influenza activity in California was widespread+ in weeks 2 and 3.
  • Outpatient ILI activity as a percentage of total visits to sentinel providers was 4.4% in week 2 and 4.9% in week 3.
  • Of the 4,921 specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories during week two, 1,376 (28.0%) were positive for influenza; of these, 57 (4.1%) were positive for influenza B and 1,319 (95.9%) were positive for influenza A. Of the influenza A specimens, 217 (16.5%) were subtyped as seasonal A (H3) and 1,102 (83.5%) were not subtyped. Of the 4,956 specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories during week three,1,439 (29.0%) were positive for influenza; of these, 65 (4.5%) were positive for influenza B and 1,374 (95.5%) were positive for influenza A. Of the influenza A specimens, 272 (19.8%) were subtyped as seasonal A (H3), 3 (0.2%) were subtyped as 2009 A (H1), and 1,099 (80.0%) were not subtyped.
  • Kaiser Permanente hospitalization data for northern and southern California showed that the percentage of hospitalizations for flu admissions, defined as a diagnosis of "flu," "influenza," or "pneumonia" recorded in text fields at time of admission, was 7.8% during week 2 and 8.8% during week 3.
  • California Department of Public Health has received nine reports of influenza-associated deaths in persons under age 65 during the 2014-2015 influenza season to date.
  • The California Department of Public Health's Influenza website contains guidance and additional data.

United States

  • Influenza activity in the United States continued at elevated levels in week 2 and week 3.
  • Some circulating H3N2 strains differ from the H3N2 component of this season's influenza vaccine. The vaccine is still recommended. CDC released additional guidance on antiviral treatment.
  • Of the 26,205 specimens tested and reported by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories during week 2, 5,104 (19.5%) were positive for influenza. During week 3, 4,651 (19.9%) tests were positive for influenza of 23,339 tests conducted.
  • The proportion of deaths due to pneumonia and influenza (P&I) was above the epidemic threshold in weeks 2 and 3.
  • Eleven influenza-associated pediatric deaths were reported during week 2. Five influenza-associated pediatric deaths were reported during week 3.
  • The proportion of outpatient visits for influenza-like illness (ILI) was 4.5% during week 2 and 4.4% during week 3.
  • All 10 regions reported a proportion of outpatient visits for ILI at or above the region-specific baseline level during weeks 2 and 3. During week 2, ILI activity was high in 23 states, moderate in New York City and 10 states, low in 10 states, and minimal in seven states. During week 3, ILI activity was high in 29 states, moderate in New York City and seven states, low in six states, and minimal in eight states.
  • During weeks 2 and 3, the geographic spread of influenza activity was reported as widespread+ in 44 states, regional* in five states, and local^ in one state. See map below for week 3.
  • For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

Geographic Distribution of Influenza in the US

+Widespread: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in at least half the regions of the state with recent laboratory evidence of influenza in the state.
*Regional: Outbreaks of influenza or increases in ILI and recent laboratory confirmed influenza in at least two but less than half the regions of the state with recent laboratory evidence of influenza in those regions
^Local: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in a single region of the state.
~Sporadic: Small numbers of laboratory-confirmed influenza cases or a single laboratory-confirmed influenza outbreak has been reported, but there is no increase in cases of ILI.

Additional flu trends can be seen in Google Flu Trends which uses aggregated Google search data in a model created in collaboration with CDC to estimate influenza activity in the United States. For more information and activity estimates from California, the U.S. and worldwide, see http://www.google.org/flutrends/

If you have any questions or comments please contact:
Jasmine Carver, MPH
Epidemiology Fellow
(415) 473-2573
JCarver@marincounty.org

This publication is provided to you by the Office of the Public Health Officer, County of Marin Department of Health and Human Services.

Sources

Centers for Disease Control and Prevention. https://www.cdc.gov/flu/weekly/ and https://www.cdc.gov/flu/weekly/weeklyarchives2014-2015/week2.htm . Accessed 1/30/2015.

California Department of Public Health. http://www.cdph.ca.gov/data/statistics/Pages/CISPDataArchive.aspx. Accessed 1/30/2015.

Marin

During week 53 (December 28-January 3) and week 1 (January 4-10), influenza was circulating in Marin County with influenza-like illness activity remaining elevated (Figure 1) and total influenza tests and specimens testing positive increasing.

Influenza-like illness activity

Influenza-like illness activity (ILI) in Marin County was moderate during week 53 (December 28-January 3) and week 1 (January 4-10). Discharge data from Kaiser San Rafael, Marin General Hospital, and Novato Community Hospital emergency departments and visits to Sutter Terra Linda Urgent Care showed the percentage of visits associated with ILI increased to 16.9% during week 53 and decreased slightly to 14.8% during week 1. See Figure 1 below. Because of the increase of ILI, emergency rooms are experiencing surges in case loads and primary care providers are encouraged to assess and treat ILI symptoms when possible.

Figure 1: Proportion of Visits due to Influenza-Like Illness (ILI): Kaiser San Rafael, MGH, and NCH Emergency Departments and Sutter Terra Linda Urgent Care, 2012-13, 2013-2014, and 2014-2015 Influenza SeasonsInfluenza-like illness, Marin County, 2012-2015

PROVISIONAL DATA, SUBJECT TO CHANGE. The case definition for ILI is any chief complaint field that includes the following keywords or variants of the keywords: influenza, flu, influenza-like illness, pneumonia, fever, cough, and/or sore throat.

We updated the influenza-like illness (ILI) syndrome definition by broadening the list of chief complaints. As a result, the weekly percentages of visits for ILI are higher throughout the year than was seen using the prior definition, but the same general patterns from previous seasons remain. We applied the improved definition to all seasons in the graph above.

Influenza testing1

During week 53, 14 (17.3%) of the 81 specimens tested for influenza were positive. During week 1, 20 (16.9%) of the 118 specimens tested for influenza were positive. The majority of specimens during week 53 and week 1 were influenza A (92% and 85%, respectively) and the remaining specimens were influenza B. As of January 10, 58 positive tests have been reported for the 2014-2015 influenza season.


Influenza Tests in Marin County, 2014-2015

1. Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, Novato Community Hospital, and Sutter Terra Linda Urgent Care.

Visit MarinFlu.org for influenza vaccination, testing, and treatment recommendations.

California

  • The geographic distribution of influenza activity in California was regional* in week 53 and widespread+ in week 1.
  • Outpatient ILI activity as a percentage of total visits to sentinel providers was 5.0% in week 53 and 4.1% in week 1.
  • Of the 3,415 specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories during week 53, 636 (18.6%) were positive for influenza; of these, 26 (4.1%) were positive for influenza B and 610 (95.9%) were positive for influenza A. Of the influenza A specimens, 126 (20.7%) were subtyped as seasonal A (H3) and 484 (79.3%) were not subtyped. Of the 4,737 specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories during week 1,161 (24.5%) were positive for influenza; of these, 53 (4.6%) were positive for influenza B and 1,108 (95.4%) were positive for influenza A. Of the influenza A specimens, 227 (20.5%) were subtyped as seasonal A (H3) and 881 (79.5%) were not subtyped.
  • Kaiser Permanente hospitalization data for northern and southern California showed that the percentage of hospitalizations for flu admissions, defined as a diagnosis of "flu," "influenza," or "pneumonia" recorded in text fields at time of admission, was 8.6% during week 53 and 7.8% during week 1.
  • California Department of Public Health has received two reports of influenza-associated deaths in persons under age 65 during the 2014-2015 influenza season to date.
  • The California Department of Public Health's Influenza website contains guidance and additional data.

United States

  • Influenza activity in the United States continued at elevated levels in week 53 and week 1.
  • Some circulating H3N2 strains differ from the H3N2 component of this season's influenza vaccine. The vaccine is still recommended. CDC released additional guidance last week on antiviral treatment.
  • Of the 30,469 specimens tested and reported by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories during week 53, 7,515 (24.7%) were positive for influenza. During week 1, 5,284 (20.2%) tests were positive for influenza of 26,204 tests conducted.
  • The proportion of deaths due to pneumonia and influenza (P&I) was above the epidemic threshold in weeks 53 and 1.
  • Five influenza-associated pediatric deaths were reported during week 53. Nineteen influenza-associated pediatric deaths were reported during week 1.
  • The proportion of outpatient visits for influenza-like illness (ILI) was 5.6% during week 53 and 4.4% during week 1.
  • All 10 regions reported a proportion of outpatient visits for ILI at or above the region-specific baseline level during weeks 53 and 1. During week 53, ILI activity was high in 26 states, moderate in New York City and eight states, low in seven states, and minimal in eight states. During week 1, ILI activity was high in 24 states, moderate in New York City and seven states, low in seven states, and minimal in eleven states.
  • During weeks 53 and 1, the geographic spread of influenza activity was reported as widespread+ in 46 states, regional* in three states, and local^ in one state. See map below for week 1.
  • For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

Geographic Distribution of Influenza in the US

+Widespread: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in at least half the regions of the state with recent laboratory evidence of influenza in the state.
*Regional: Outbreaks of influenza or increases in ILI and recent laboratory confirmed influenza in at least two but less than half the regions of the state with recent laboratory evidence of influenza in those regions
^Local: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in a single region of the state.
~Sporadic: Small numbers of laboratory-confirmed influenza cases or a single laboratory-confirmed influenza outbreak has been reported, but there is no increase in cases of ILI.

Additional flu trends can be seen in Google Flu Trends which uses aggregated Google search data in a model created in collaboration with CDC to estimate influenza activity in the United States. For more information and activity estimates from California, the U.S. and worldwide, see http://www.google.org/flutrends/

If you have any questions or comments please contact:
Jasmine Carver, MPH
Epidemiology Fellow
(415) 473-2573
JCarver@marincounty.org

This publication is provided to you by the Office of the Public Health Officer, County of Marin Department of Health and Human Services.

Sources

Centers for Disease Control and Prevention. https://www.cdc.gov/flu/weekly/ and https://www.cdc.gov/flu/weekly/weeklyarchives2014-2015/week53.htm. Accessed 1/21/2015.

California Department of Public Health. http://www.cdph.ca.gov/data/statistics/Pages/CISPDataArchive.aspx. Accessed 1/21/2015.

Marin

During week 51 (December 14-20) and week 52 (December 21-27), influenza-like illness activity began increasing in Marin (Figure 1). Compared with prior weeks this season, more influenza tests were conducted and more specimens were positive during week 52. While the percent positive has not increased from prior weeks, this should serve as a reminder to all providers that it's not too late to discuss and offer immunization to our not yet vaccinated patient population.

Influenza-like illness activity

Influenza-like illness activity in Marin County was low during week 51 (December 14-20) and moderate during week 52 (December 21-27). Discharge data from Kaiser San Rafael, Marin General Hospital, and Novato Community Hospital emergency departments and visits to Sutter Terra Linda Urgent Care showed the percentage of visits associated with influenza-like illness (ILI) increased to 11.2% during week 51 and 15.8% during week 52. See Figure 1 below.

Figure 1: Proportion of Visits due to Influenza-Like Illness (ILI): Kaiser San Rafael, MGH, and NCH Emergency Departments and Sutter Terra Linda Urgent Care, 2012-13, 2013-2014, and 2014-2015 Influenza SeasonsInfluenza-like illness, Marin County, 2012-2015

PROVISIONAL DATA, SUBJECT TO CHANGE. The case definition for ILI is any chief complaint field that includes the following keywords or variants of the keywords: influenza, flu, influenza-like illness, pneumonia, fever, cough, and/or sore throat.

We updated the influenza-like illness (ILI) syndrome definition by broadening the list of chief complaints. As a result, the weekly percentages of visits for ILI are higher throughout the year than was seen using the prior definition, but the same general patterns from previous seasons remain. We applied the improved definition to all seasons in the graph above.

Influenza testing1

During week 51, 3 (8.1%) of the 37 specimens tested for influenza were positive. During week 52, 6 (9.1%) of the 66 specimens tested for influenza were positive. All positive specimens during weeks 51 and 52 were influenza A. During this influenza season through December 27, 24 specimens have tested positive for influenza.


Influenza Tests in Marin County, 2014-2015

1. Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, Novato Community Hospital, and Sutter Terra Linda Urgent Care.

Visit MarinFlu.org for influenza vaccination, testing, and treatment recommendations.

California

  • A report covering California influenza activity during weeks 51 and 52 has not yet been released.
  • The California Department of Public Health's Influenza website contains guidance and additional data.

United States

  • Influenza activity in the United States continued increasing in weeks 51 and 52.
  • Some circulating H3N2 strains differ from the H3N2 component of this season's influenza vaccine. The vaccine is still recommended. CDC's indications for antiviral therapy are here.
  • Of the 21,858 specimens tested and reported by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories during week 51, 6,152 (28.1%) were positive for influenza. Of the 24,001 specimens tested and reported during week 52, 7,289 (30.4%) were positive for influenza.
  • The proportion of deaths due to pneumonia and influenza (P&I) was at the epidemic threshold in week 51 and below the epidemic threshold in week 52.
  • Four influenza-associated pediatric deaths were reported during week 51 and six were reported during week 52.
  • The proportion of outpatient visits for influenza-like illness (ILI) was 5.5% during week 51 and 5.9% during week 52.
  • All 10 regions reported a proportion of outpatient visits for ILI at or above the region-specific baseline level during weeks 51 and 52. ILI activity was high in 22 states, moderate in six states, low in New York City and eight states, and minimal in 14 states during week 51. ILI activity was high in 29 states, moderate in New York City and six states, low in five states, and minimal in nine states during week 52.
  • During week 51, the geographic spread of influenza activity was reported as widespread+ in 36 states, regional* in 10 states, local^ in two states, and sporadic~ in two states. During week 52, the geographic spread of influenza activity was reported as widespread+ in 43 states, regional* in six states, and sporadic~ in one state. See map below for week 52.
  • For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

Geographic Distribution of Influenza in the US

+Widespread: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in at least half the regions of the state with recent laboratory evidence of influenza in the state.
*Regional: Outbreaks of influenza or increases in ILI and recent laboratory confirmed influenza in at least two but less than half the regions of the state with recent laboratory evidence of influenza in those regions
^Local: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in a single region of the state.
~Sporadic: Small numbers of laboratory-confirmed influenza cases or a single laboratory-confirmed influenza outbreak has been reported, but there is no increase in cases of ILI.

Additional flu trends can be seen in Google Flu Trends which uses aggregated Google search data in a model created in collaboration with CDC to estimate influenza activity in the United States. For more information and activity estimates from California, the U.S. and worldwide, see http://www.google.org/flutrends/

If you have any questions or comments please contact:
Jessica Cunningham-Krahl, MPH
Epidemiologist
(415) 473-7346
JCunningham@marincounty.org

This publication is provided to you by the Office of the Public Health Officer, County of Marin Department of Health and Human Services.

Sources

Centers for Disease Control and Prevention. https://www.cdc.gov/flu/weekly/ and https://www.cdc.gov/flu/weekly/weeklyarchives2014-2015/week51.htm. Accessed 1/8/2015.

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