Influenza Activity Updates | Marin Health and Human Services

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.

Influenza Surveillance Update, Two weeks ending January 23, 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 Seasons Influenza-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

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.

⁺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. https://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%2002%20-%20FINAL%20Report.pdf and https://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.

Influenza Surveillance Update, Two weeks ending January 9, 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.

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

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.

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 https://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.

Influenza Surveillance Update, Two weeks ending December 26, 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.

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

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.

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.

Influenza Surveillance Update, Two weeks ending December 12, 2015

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.

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

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.

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%2049%20-%20FINAL%20Report.pdf and https://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.

Influenza Surveillance Update - Week ending November 28, 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 Seasons

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

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.

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/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.

Influenza Surveillance Update, Two weeks ending March 21

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 Seasons Influenza-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

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.

⁺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.

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. https://www.cdph.ca.gov/data/statistics/Pages/CISPDataArchive.aspx. Accessed 3/31/2015.

Influenza Surveillance Update, Two weeks ending March 7

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.

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.

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.

⁺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.

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. https://www.cdph.ca.gov/data/statistics/Pages/CISPDataArchive.aspx. Accessed 3/18/2015.

Influenza Surveillance Update, Two weeks ending February 21

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.

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

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.

⁺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.

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. https://www.cdph.ca.gov/data/statistics/Pages/CISPDataArchive.aspx. Accessed 3/3/2015.

Influenza Surveillance Update, Two weeks ending February 7

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.

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.

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.

⁺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.

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. https://www.cdph.ca.gov/data/statistics/Pages/CISPDataArchive.aspx. Accessed 2/17/2015.

Influenza Surveillance Update, Two weeks ending January 24

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.

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.

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.

⁺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.

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. https://www.cdph.ca.gov/data/statistics/Pages/CISPDataArchive.aspx. Accessed 1/30/2015.

Influenza Surveillance Update, Two weeks ending January 10

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 Seasons Influenza-like illness, Marin County, 2012-2015

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.

⁺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.

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. https://www.cdph.ca.gov/data/statistics/Pages/CISPDataArchive.aspx. Accessed 1/21/2015.

Influenza Surveillance Update - Two weeks ending December 27, 2014

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.

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.

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.

Influenza Surveillance Update - Week ending December 13, 2014

Marin

During the first eleven weeks of the 2014-2015 influenza season (September 28-December 13), influenza activity in Marin remained minimal and within expected levels for early in the season.

Influenza-like illness activity:

We updated the influenza-like illness (ILI) syndrome definition by broadening the list of chief complaints. The weekly percentages of visits for ILI are higher throughout the year than the prior definition, but the same general patterns from prior years remain. We applied the improved definition to all seasons in the graph below (Figure 1).

Influenza-like illness activity in Marin County was minimal during week 50 (December 7 - 13, 2014). 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 8.61% during week 50. See Figure 1 below.

Influenza testing¹: During week 50, 3 (9.1%) of the 33 specimens tested for influenza were positive. All positive specimens during week 50 were influenza A. During this influenza season through December 13, 15 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

During week 50, the geographic distribution of influenza activity in California was regional*.
Outpatient ILI activity as a percentage of total visits to sentinel providers was 2.3% in week 50.
Of the 1,793 specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories during week 50, 246 (13.7%) were positive for influenza; of these, 36 (14.6%) were positive for influenza B and 210 (85.4%) were positive for influenza A. Of the influenza A specimens, 57 (27.1%) were subtyped as seasonal A (H3) and 153 (72.9%) 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 50.
No specimens from California residents have been strain-typed this season.
California Department of Public Health has not received 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 was increasing in week 50.
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 20,064 specimens tested and reported by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories during week 50, 5,200 (25.9%) were positive for influenza.
The proportion of deaths due to pneumonia and influenza (P&I) was below the epidemic threshold.
Four influenza-associated pediatric deaths were reported during week 50.
The proportion of outpatient visits for influenza-like illness (ILI) was 3.7% during week 50.
Nine of 10 regions reported a proportion of outpatient visits for ILI at or above the region-specific baseline level during week 50. ILI activity was high in 13 states, moderate in six states, low in New York City and five states, and minimal in 26 states during week 50.
During week 50, the geographic spread of influenza activity was reported as widespread⁺; in 29 states, regional* in 14 states, local^ in five states, and sporadic^~in two states. 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.

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

California Department of Public Health. http://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%20201445%20-%20FINAL%20Report.pdf. Accessed 12/22/2014.

Centers for Disease Control and Prevention. http://www.cdc.gov/flu/weekly/. Accessed 12/23/2014.

Influenza Surveillance Update, Two weeks ending February 15th

Due to decreasing influenza activity, this is the final report for the 2013-2014 influenza season. The first report of the 2014-2015 influenza season will be published in October 2014.

Marin

Severe influenza: Influenza deaths and ICU admissions for persons under age 65 years are reportable events. County of Marin Department of Health and Human Services has received reports for the following severe influenza cases in Marin County residents as of 2/24/2014:

2 laboratory-confirmed influenza-associated deaths in persons under age 65
No persons under age 65 with laboratory-confirmed influenza are currently in intensive care

Influenza-like illness activity: Influenza-like illness activity in Marin County was moderate during week 6 (February 2-8) and week 7 (February 9-15. Discharge data from Kaiser San Rafael, Marin General Hospital, and Novato Community Hospital emergency departments showed the percentage of visits associated with influenza-like illness (ILI) was 1.50% during week 6 and 1.11% during week 7.

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

Influenza testing¹: During week 6, 17 (22.4%) of the 76 specimens tested for influenza were positive. During week 7, 8 (9.6%) of the 83 specimens tested for influenza were positive. All positive tests during weeks 6 and 7 were influenza A. During this influenza season through February 15, 247 specimens have tested positive for influenza.

Subtyping has been performed on 59 influenza A specimens from Marin facilities this season through February 15th. Fifty (84.7%) were subtyped as H1N1 and nine (15.3%) were subtyped as seasonal H3.

1. Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, Novato Community Hospital, and Solano-Napa-Yolo-Marin Public Health Lab.

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

California

During weeks 6 and 7, the geographic distribution of influenza activity in California was widespread*.
Outpatient ILI activity as a percentage of total visits to sentinel providers was 4.6% in week 6 and 3.7% in week 7.
Of the 3,957 specimens tested by the Respiratory Laboratory Network (RLN) and sentinel laboratories during week 6, 848 (21.4%) were positive for influenza; of these, 140 (16.5%) were positive for influenza B and 708 (83.5%) were positive for influenza A. Of the influenza A specimens, 27 (3.8%) were subtyped as seasonal A (H3), 379 (53.5%) were subtyped as 2009 A (H1), and 302 (42.7%) were not subtyped. During week 7, 396 (13.2%) of 3,007 specimens tested for influenza were positive. Of these, 96 (24.2%) were positive for influenza B and 300 (75.8%) were positive for influenza A. Of the influenza A specimens, 29 (9.7%) were subtyped as seasonal A (H3), 121 (40.3%) were subtyped as 2009 A (H1), and 150 (50.0%) 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 7.0% during week 6 and 5.7% during week 7.
Thirty-five specimens from California residents have been strain-typed this season; all matched components of the 2013-2014 influenza vaccine.
California Department of Public Health received 41 reports of influenza-associated deaths in persons under age 65 during week 6 and 35 during week 7. During the 2013–2014 influenza season through week 7, 278 laboratory-confirmed influenza-associated death in a person under age 65 has been reported in California. Preliminary data show 29 additional laboratory-confirmed influenza-associated deaths in persons under age 65 reported after week 7.
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 weeks 6 and 7.
Of the 7,562 specimens tested by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories and reported to CDC/Influenza Division during week 6, 1,268 (16.8%) were positive for influenza. During week 7, 958 (13.9%) of tests were positive for influenza.
The proportion of deaths due to pneumonia and influenza (P&I) was 8.4% in week 6 and 8.2% in week 7.
Ten influenza-associated pediatric deaths were reported during week 6. Two pediatric deaths were reported in week 7.
The proportion of outpatient visits for influenza-like illness (ILI) was 3.0% during week 6 and 2.5% during week 7.
All ten regions reported a proportion of outpatient visits for ILI above the region-specific baseline level during week 6. ILI activity was high in six states, moderate in seven states, low in New York City and 19 states, and minimal in 18 states during week 6. Nine of the ten regions reported a proportion of outpatient visits for ILI above the region-specific baseline level during week 7. ILI activity was moderate in seven states, low in New York City and 16 states, and minimal in 27 states during week 7.
During week 6, the geographic spread of influenza activity was reported as widespread* in 24 states, regional^ in 20 states, local^~ in five states, and sporadic^# in one state. During week 7, the geographic spread of influenza activity was reported as widespread* in 17 states, regional^ in 22 states, local~ in nine states, and sporadic# in two states. See map below.
For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

geographic spread of influenza map by state, week 7

* 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.

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

California Department of Public Health. https://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%207%20-%20FINAL%20Report.pdf and https://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%206%20-%20FINAL%20Report_Updated.pdf. Accessed 2/24/2014.

Centers for Disease Control and Prevention. https://www.cdc.gov/flu/weekly/ and http://www.cdc.gov/flu/weekly/weeklyarchives2013-2014/weekly6.html Accessed 2/26/2014.

Influenza Surveillance Update, Week ending February 1st

Marin

2 laboratory-confirmed influenza-associated deaths in persons under age 65
No persons under age 65 with laboratory-confirmed influenza are currently in intensive care

Influenza-like illness activity: Influenza-like illness activity in Marin County was moderate during week 5 (January 26 - February 1). Discharge data from Kaiser San Rafael, Marin General Hospital, and Novato Community Hospital emergency departments and visits to the Sutter Terra Linda Urgent Care Center showed the percentage of visits associated with influenza-like illness (ILI) decreased to 1.38% during 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 Clinic, 2011-12, 2012-2013, and 2013-2014 Influenza Seasons

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

Influenza testing¹: During week 5, 30 (19.2%) of the 156 specimens tested for influenza were positive. Of the positive specimens during week 5, 25 (83.3%) were influenza A and 5 (16.7%) was influenza B. During this influenza season through February 1, 222 specimens have tested positive for influenza.

Subtyping has been performed on 48 influenza A specimens from Marin facilities this season through January 21. Forty-five (93.8%) were subtyped as H1N1 and three (6.3%) were subtyped as seasonal H3.

1. Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, Novato Community Hospital, and Solano-Napa-Yolo-Marin Public Health Lab.

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

California

During week 5, the geographic distribution of influenza activity in California was widespread*.
Outpatient ILI activity as a percentage of total visits to sentinel providers was 4.6% in week 5.
Of the 4,438 specimens tested by the Respiratory Laboratory Network (RLN) and sentinel laboratories during week 5, 1,211 (27.3%) were positive for influenza; of these, 184 (4.1%) were positive for influenza B and 1,027 (23.1%) were positive for influenza A. Of the influenza A specimens, 33 (3.2%) were subtyped as seasonal A (H3), 509 (49.6%) were subtyped as 2009 A (H1), and 486 (47.3%) 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 7.3% during week 5.
Twenty-eight specimens from California residents have been strain-typed this season; all matched components of the 2013-2014 influenza vaccine.
California Department of Public Health received 56 reports of influenza-associated deaths in persons under age 65 during week 5. During the 2013–2014 influenza season through week 5, 202 laboratory-confirmed influenza-associated death in a person under age 65 has been reported in California. Preliminary data show 41 additional laboratory-confirmed influenza-associated deaths in persons under age 65 reported after week 5.
The California Department of Public Health's Influenza website contains guidance and additional data.

United States

Influenza activity in the United States remained high in week 5.
Of the 8,282 specimens tested by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories and reported to CDC/Influenza Division during week 5, 1,626 (19.6%) were positive for influenza.
The proportion of deaths due to pneumonia and influenza (P&I) was 8.6% in week 5.
Three influenza-associated pediatric deaths were reported during week 5.
The proportion of outpatient visits for influenza-like illness (ILI) was 3.2% during week 5.
All ten regions reported a proportion of outpatient visits for ILI above the region-specific baseline level during week 5. ILI activity was high in seven states, moderate 12 states, low in New York City and in 14 states, and minimal in 17 states during week 5.
During week 5, the geographic spread of influenza activity was reported as widespread* in 29 states, regional^ in 19 states, local^~ in one state, and sporadic^# in one state. See map below.
For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

If you have any questions or comments please contact:
Jessica Cunningham, 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

California Department of Public Health. https://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%203%20-%20FINAL%20Report.pdf. Accessed 2/12/2014.

Centers for Disease Control and Prevention. http://www.cdc.gov/flu/weekly/. Accessed 2/12/2014.

Influenza Surveillance Update, Week ending January 25th

Marin

2 laboratory-confirmed influenza-associated deaths in persons under age 65
No persons under age 65 with laboratory-confirmed influenza are currently in intensive care

Influenza-like illness activity: Influenza-like illness activity in Marin County was moderate during week 4 (January 19-25). Discharge data from Kaiser San Rafael, Marin General Hospital, and Novato Community Hospital emergency departments and visits to the Sutter Terra Linda Urgent Care Center showed the percentage of visits associated with influenza-like illness (ILI) increased to 2.16% during week 4. See Figure 1 below.

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

Influenza testing¹: During week 4, 23 (19.5%) of the 118 specimens tested for influenza were positive. Of the positive specimens during week 4, 22 (95.7%) were influenza A and 1 (4.3%) was influenza B. During this influenza season through January 25, 192 specimens have tested positive for influenza.

Subtyping has been performed on 48 influenza A specimens from Marin facilities this season through January 21. Forty-five (93.8%) were subtyped as H1N1 and three (6.3%) were subtyped as seasonal H3.

1. Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, Novato Community Hospital, and Solano-Napa-Yolo-Marin Public Health Lab.

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

California

During week 4, the geographic distribution of influenza activity in California was widespread*.
Outpatient ILI activity as a percentage of total visits to sentinel providers was 5.0% in week 4.
Of the 5,100 specimens tested by the Respiratory Laboratory Network (RLN) and sentinel laboratories during week 4, 1,493 (29.3%) were positive for influenza; of these, 153 (3.0%) were positive for influenza B and 1,340 (26.3%) were positive for influenza A. Of the influenza A specimens, 22 (1.6%) were subtyped as seasonal A (H3), 564 (42.1%) were subtyped as 2009 A (H1), and 754 (56.3%) 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 7.3% during week 4.
Twenty-eight specimens from California residents have been strain-typed this season; all matched components of the 2013-2014 influenza vaccine.
California Department of Public Health received 54 reports of influenza-associated deaths in persons under age 65 during week 4. During the 2013–2014 influenza season through week 4, 147 laboratory-confirmed influenza-associated death in a person under age 65 has been reported in California. Preliminary data show 44 additional laboratory-confirmed influenza-associated deaths in persons under age 65 reported after week 4.
The California Department of Public Health's Influenza website contains guidance and additional data.

United States

Influenza activity in the United States remained high in week 4.
Of the 9,514 specimens tested by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories and reported to CDC/Influenza Division during week 4, 2,006 (21.1%) were positive for influenza.
The proportion of deaths due to pneumonia and influenza (P&I) was 8.8% in week 4.
Nine influenza-associated pediatric deaths were reported during week 4.
The proportion of outpatient visits for influenza-like illness (ILI) was 3.3% during week 4.
All ten regions reported a proportion of outpatient visits for ILI above the region-specific baseline level during week 4. ILI activity was high in 10 states, moderate in New York City and 12 states, low in 14 states, and minimal in 14 states during week 4.
During week 4, the geographic spread of influenza activity was reported as widespread* in 38 states, regional^ in 10 states, local^~ in one state, and sporadic^# in one state. See map below.
For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

US Geographic Distribution of Influenza, week 4

If you have any questions or comments please contact:
Jessica Cunningham, 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

California Department of Public Health. https://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%203%20-%20FINAL%20Report.pdf. Accessed 2/4/2014.

Centers for Disease Control and Prevention. http://www.cdc.gov/flu/weekly/. Accessed 2/4/2014.

Influenza Surveillance Update, Week ending January 18th

Marin

2 laboratory-confirmed influenza-associated deaths in persons under age 65
No persons under age 65 with laboratory-confirmed influenza are currently in intensive care

Influenza-like illness activity: Influenza-like illness activity in Marin County was moderate during week 3 (January 12-18). Discharge data from Kaiser San Rafael, Marin General Hospital, and Novato Community Hospital emergency departments and visits to the Sutter Terra Linda Urgent Care Center showed the percentage of visits associated with influenza-like illness (ILI) increased to 1.22% during week 3. See Figure 1 below.

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

Influenza testing¹: During week 3, 39 (22.2%) of the 176 specimens tested for influenza were positive. Of the positive specimens during week 3, 38 (97.4%) were influenza A and 1 (2.6%) was influenza B. During this influenza season through January 18, 169 specimens have tested positive for influenza.

Subtyping has been performed on 48 influenza A specimens from Marin facilities this season through January 21. Forty-five (93.8%) were subtyped as H1N1 and three (6.3%) were subtyped as seasonal H3.

1. Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, Novato Community Hospital, and Solano-Napa-Yolo-Marin Public Health Lab.

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

California

During week 3, the geographic distribution of influenza activity in California was widespread*.
Outpatient ILI activity as a percentage of total visits to sentinel providers was 4.3% in week 3.
Of the 4,576 specimens tested by the Respiratory Laboratory Network (RLN) and sentinel laboratories during week 3, 1,389 (30.4%) were positive for influenza; of these, 81 (1.8%) were positive for influenza B and 1,308 (28.6%) were positive for influenza A. Of the influenza A specimens, 15 (1.1%) were subtyped as seasonal A (H3), 415 (31.7%) were subtyped as 2009 A (H1), and 878 (67.1%) 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 3.
Twenty-five specimens from California residents have been strain-typed this season; all matched components of the 2013-2014 influenza vaccine.
California Department of Public Health received 50 reports of influenza-associated deaths in persons under age 65 during week 3. During the 2013–2014 influenza season through week 3, 95 laboratory-confirmed influenza-associated death in a person under age 65 has been reported in California. Preliminary data show 51 additional laboratory-confirmed influenza-associated deaths in persons under age 65 reported after week 3.
The California Department of Public Health's Influenza website contains guidance and additional data.

United States

Influenza activity in the United States remained high in week 3.
Of the 12,108 specimens tested by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories and reported to CDC/Influenza Division during week 3, 2,793 (23.1%) were positive for influenza.
The proportion of deaths due to pneumonia and influenza (P&I) was 8.1% in week 3.
Eight influenza-associated pediatric deaths were reported during week 3.
The proportion of outpatient visits for influenza-like illness (ILI) was 3.4% during week 3.
All ten regions reported a proportion of outpatient visits for ILI above the region-specific baseline level during week 3. ILI activity was high in 13 states, moderate in New York City and seven states, low in 15 states, and minimal in 15 states during week 3.
During week 3, the geographic spread of influenza activity was reported as widespread* in 41 states, regional^ in eight states, local^~ in no states, and sporadic^# in one state. See map below.
For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

US Geographic Distribution of Influenza, week 3

If you have any questions or comments please contact:
Jessica Cunningham, 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

California Department of Public Health. https://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%203%20-%20FINAL%20Report.pdf. Accessed 1/24/2014.

Centers for Disease Control and Prevention. http://www.cdc.gov/flu/weekly/. Accessed 1/29/2014.

Influenza Surveillance Update, Two weeks ending January 11th

Marin

2 laboratory-confirmed influenza-associated deaths in persons under age 65
No persons under age 65 with laboratory-confirmed influenza are currently in intensive care

Influenza-like illness activity: Influenza-like illness activity in Marin County was low during week 1 (December 29-January 4) and moderate during week 2 (January 5-11). Discharge data from Kaiser San Rafael, Marin General Hospital, and Novato Community Hospital emergency departments and visits to the Sutter Terra Linda Urgent Care Center showed the percentage of visits associated with influenza-like illness (ILI) decreased to 0.55% during week 1 and increased to 1.09% during week 2. See Figure 1 below.

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

Influenza testing¹: During week 1, 25 (28.7%) of the 87 specimens tested for influenza were positive. All of the positive specimens were influenza A. During week 2, 44 (28.2%) of the 156 specimens tested were positive. Of the positive specimens during week 2, 42 (95.5%) were influenza A and 2 (4.5%) were influenza B. During this influenza season through January 11, 127 specimens have tested positive for influenza.

Subtyping has been performed on 48 influenza A specimens from Marin facilities this season through January 21. Forty-five (93.8%) were subtyped as H1N1 and three (6.3%) were subtyped as seasonal H3.

1. Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, Novato Community Hospital, and Solano-Napa-Yolo-Marin Public Health Lab.

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

California

During weeks 1 and 2, the geographic distribution of influenza activity in California was widespread*.
Outpatient ILI activity as a percentage of total visits to sentinel providers was 5.4% in week 1 and 4.5% in week 2.
Of the 3,431 specimens tested by the Respiratory Laboratory Network (RLN) and sentinel laboratories during week 1, 980 (28.6%) were positive for influenza; of these, 34 (3.5%) were positive for influenza B and 946 (96.5%) were positive for influenza A. Of the influenza A specimens, 11 (1.2%) were subtyped as seasonal A (H3), 249 (26.3%) were subtyped as 2009 A (H1), and 686 (72.5%) were not subtyped. Of the 4,441 specimens tested during week 2, 1,463 (32.9%) were positive for influenza; of these, 43 (2.9%) were influenza B and 1,420 (97.1%) were influenza A. Of the influenza A specimens, 15 (1.1%) were subtyped as seasonal A (H3), 419 (29.5%) were subtyped as 2009 A (H1), and 986 (69.4%) 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 9.4% during week 1 and 8.8% during week 2.
Sixteen specimens from California residents have been strain-typed this season; all matched components of the 2013-2014 influenza vaccine.
California Department of Public Health received three reports of influenza-associated deaths in persons under age 65 during week 1 and 38 deaths during week 2. During the 2013–2014 influenza season through week 2, 45 laboratory-confirmed influenza-associated death in a person under age 65 has been reported in California. Preliminary data show 50 additional laboratory-confirmed influenza-associated deaths in persons under age 65 reported after week 2.
The California Department of Public Health's Influenza website contains guidance and additional data.

United States

Influenza activity in the United States continued to increase during week 1 and remained high in week 2.
Of the 9,482 specimens tested by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories and reported to CDC/Influenza Division during week 1, 2,486 (26.2%) were positive for influenza. Of the 10,841 specimens tested and reported during week 2, 2,721 (25.1%) were positive for influenza.
The proportion of deaths due to pneumonia and influenza (P&I) was 6.9% in week 1 and 7.5% in week 2.
Four influenza-associated pediatric deaths were reported during week 1. Ten pediatrics deaths were reported during week 2.
The proportion of outpatient visits for influenza-like illness (ILI) was 4.4% during week 1 and 3.6% during week 2, exceeding the national baseline of 2.0%.
All ten regions reported a proportion of outpatient visits for ILI at or above the region-specific baseline level during week 1. ILI activity was high in 20 states, moderate in New York City and seven states, low in 11 states, and minimal in 12 states during week 1. All ten regions reported a proportion of outpatient visits for ILI above the region-specific baseline level during week 2. ILI activity was high in 14 states, moderate in 12 states, low in New York City and eight states, and minimal in 16 states during week 2.
During week 1, the geographic spread of influenza activity was reported as widespread* in 36 states, regional^ in 11 states, local^~ in two states, and sporadic^# in one state. During week 2, the geographic spread of influenza activity was reported as widespread* in 40 states, regional^ in nine states, and sporadic^# in one state. See map for week 2 below.
For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

US Geographic Distribution of Influenza, week 2

If you have any questions or comments please contact:
Jessica Cunningham, 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

California Department of Public Health. https://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%201%20-%20FINAL%20Report.pdf. Accessed 1/10/2014.

California Department of Public Health. https://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%202%20-%20FINAL%20Report.pdf. Accessed 1/22/2014

Centers for Disease Control and Prevention. https://www.cdc.gov/flu/weekly/weeklyarchives2013-2014/weekly1.html. Accessed 1/17/2014.

Centers for Disease Control and Prevention. http://www.cdc.gov/flu/weekly/. Accessed 1/22/2014.

Influenza Surveillance Update, Week ending December 28th

Marin

Influenza-like illness activity: Influenza-like illness activity in Marin County from December 22-28 was low. Discharge data from Kaiser San Rafael, Marin General Hospital, and Novato Community Hospital emergency departments and visits to the Sutter Terra Linda Urgent Care Center showed the percentage of visits associated with influenza-like illness (ILI) increased to 0.99% during week 52. See Figure 1 below.

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

Influenza testing¹: During week 52, 23 (28.8%) of the 80 specimens tested for influenza were positive. Of the positive tests, 22 (95.7%) were influenza A and one (4.3%) was influenza B. During the 2013-2014 influenza season through December 28, 58 specimens have tested positive for influenza.

1. Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, Novato Community Hospital, and Solano-Napa-Yolo-Marin Public Health Lab.

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

California

California Department of Public Health released an update about severe influenza.
During week 52, the geographic distribution of influenza activity in California was regional^.
Outpatient ILI activity as a percentage of total visits to sentinel providers was 3.4% in week 52.
Of the 1,945 specimens tested by the Respiratory Laboratory Network (RLN) and sentinel laboratories during week 52, 442 (22.7%) were positive for influenza; of these, 23 (5.2%) were positive for influenza B and 419 (94.8%) were positive for influenza A. Of the influenza A specimens, three (0.7%) were subtyped as seasonal A (H3), 72 (17.2%) were subtyped as 2009 A (H1), and 344 (82.1%) 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 52.
Eleven specimens from California residents have been strain-typed this season; all matched components of the 2013-2014 influenza vaccine.
California Department of Public Health received no reports of influenza-associated deaths in persons under age 65 during week 52. During the 2013–2014 influenza season, four laboratory-confirmed influenza-associated death in a person under age 65 has been reported in California.
The California Department of Public Health's Influenza Surveillance website contains information about their program.

United States

Influenza activity in the United States continued to increase during week 52.
Of the 6,419 specimens tested by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories and reported to CDC/Influenza Division during week 52, 1,711 (26.7%) were positive for influenza.
The proportion of deaths due to pneumonia and influenza (P&I) was 6.5% in week 52, which were below the epidemic threshold for the week.
Two influenza-associated pediatric deaths were reported during week 52 for deaths that occurred in week 50 and week 51.
The proportion of outpatient visits for influenza-like illness (ILI) was 4.3% during week 52, exceeding the national baseline of 2.0%.
All ten regions reported a proportion of outpatient visits for ILI at or above the region-specific baseline level during week 52. ILI activity was high in 20 states, moderate in New York City and eight states, low in six states, and minimal in 16 states during week 52.
During week 52, the geographic spread of influenza activity was reported as widespread* in 25 states, regional^ in 20 states, local^~ in three states, and sporadic^# in two states. See map below.
For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

US Geographic Distribution of Influenza, week 52

If you have any questions or comments please contact:
Jessica Cunningham, 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

California Department of Public Health. http://www.cdph.ca.gov/programs/dcdc/Documents/Week%2052%20-%20FINAL%20Report.pdf. Accessed 1/6/2014.

Centers for Disease Control and Prevention. http://cdc.gov/flu/weekly/. Accessed 1/7/2014.

Influenza Surveillance Update, Two weeks ending December 21st

Marin

Influenza-like illness activity: Influenza-like illness activity in Marin County from December 8-21 was low. Discharge data from Kaiser San Rafael, Marin General Hospital, and Novato Community Hospital emergency departments and visits to the Sutter Terra Linda Urgent Care Center showed the percentage of visits associated with influenza-like illness (ILI) increased to 0.83% during week 50 (December 8-14, 2013) and decreased to 0.60% in week 51 (December 15-21). See Figure 1 below.

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

Influenza testing¹: During week 50, six (15.0%) of the 40 specimens tested for influenza were positive. Of the 59 specimens tested for influenza during week 51, 12 (20.3%) tested positive. All positive tests in both weeks were influenza A viruses. To date during the 2013-2014 influenza season, 35 specimens have tested positive for influenza. The elevated percentages since week 49 suggest that influenza virus may be circulating locally.

Although subtyping is not routinely performed on each positive specimen in Marin, two specimens were subtyped during week 50 and eight specimens during week 51; all were 2009 H1N1. Marin's subtyping results are consistent with current California and United States patterns of nearly all influenza A specimens with subtyping performed being 2009 H1N1.

1. Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, Novato Community Hospital, and Solano-Napa-Yolo-Marin Public Health Lab.

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

California

During week 50, the geographic distribution of influenza activity in California was local^~.
Outpatient ILI activity as a percentage of total visits to sentinel providers was 2.5% in week 50.
Of the 1,249 specimens tested by the Respiratory Laboratory Network (RLN) and sentinel laboratories during week 50, 108 (8.6%) were positive for influenza; of these, seven (6.5%) were positive for influenza B and 101 (93.5%) were positive for influenza A. Of the influenza A specimens, two (2.0%) were subtyped as seasonal A (H3), 51 (50.5%) were subtyped as 2009 A (H1), and 48 (47.5%) 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 4.8% during week 50.
Ten specimens from California residents have been strain-typed this season; all matched components of the 2013-2014 influenza vaccine.
California Department of Public Health received no reports of influenza-associated deaths in persons under age 65 during week 50. During the 2013–2014 influenza season, two laboratory-confirmed influenza-associated death in a person under age 65 has been reported in California.
Data for week 51 are not yet available.
The California Department of Public Health's Influenza Surveillance website contains information about their program.

United States

Influenza activity in the United States continued to increase during weeks 50 and 51.
Of the 7,294 specimens tested by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories and reported to CDC/Influenza Division during week 50, 1,301 (17.8%) were positive for influenza. During week 51, 1,639 (24.1%) tests were positive for influenza of 6,813 tests conducted.
The proportion of deaths due to pneumonia and influenza (P&I) was 6.6% in week 50 and 6.7% in week 51, which were below the epidemic threshold for each week.
One influenza-associated pediatric death was reported during week 50 for a death that occurred in that week.
The proportion of outpatient visits for influenza-like illness (ILI) was 2.3% during week 50 and 3.0% during week 51, exceeding the national baseline of 2.0%.
Five regions reported a proportion of outpatient visits for ILI at or above the region-specific baseline level during week 50 and eight regions reached or exceeded their baseline level during week 51. ILI activity was high in four states, moderate in one state, low in New York City and six states, and minimal in 37 states during week 50. Data were insufficient in two states. ILI activity was high in six states, moderate in eight states, low in six states, and minimal in 28 states during week 51. Data were insufficient in New York City and two states.
During week 50, the geographic spread of influenza activity was reported as widespread* in four states, regional^ in 20 states, local^~ in 17 states, and sporadic^# in 8 states. One state reported no influenza activity. During week 51, the geographic spread of influenza activity was reported as widespread* in 10 states, regional^ in 23 states, local^~ in 12 states, and sporadic^# in four states. One state did not report. See map for week 51 below.
For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

US Geographic Distribution of Influenza, week 51

If you have any questions or comments please contact:
Jessica Cunningham, 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

California Department of Public Health. http://www.cdph.ca.gov/programs/dcdc/Documents/Week%2050%20-%20FINAL%20Report.pdf. Accessed 12/30/2013.

Centers for Disease Control and Prevention. http://cdc.gov/flu/weekly/ and http://www.cdc.gov/flu/weekly/weeklyarchives2013-2014/weekly50.html. Accessed 12/30/2013.

Severe Influenza Reported Nationally

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