Influenza Activity Updates

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

Influenza Surveillance Update, Two weeks ending December 7th

Marin

Influenza-like illness activity: Influenza-like illness activity in Marin County from November 24-December 7 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 0.84% during week 48 (November 24-30, 2013) and decreased to 0.56% in week 49 (December 1-7). See Figure 1 below.

Figure 1: Proportion of Visits due to Influenza-Like Illness (ILI): Kaiser San Rafael, MGH, and NCH Emergency Departments and Sutter Terra Linda Urgent Care Clinic, 2011-12, 2012-2013, and 2013-2014 Influenza Seasons Marin Influenza-like illness 2011-2013

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 48, two (7.4%) of the 27 specimens tested for influenza were positive. Of the 39 specimens tested for influenza during week 49, six (15.4%) tested positive. All positive tests in both weeks were influenza A viruses. To date during the 2013-2014 influenza season, 17 specimens have tested positive for influenza. The elevated percentage during week 49 and preliminary data showing similar percentages for week 50 suggest that influenza virus may be circulating locally.

1. Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, and Novato Community Hospital.

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

California

During weeks 48 and 49, the geographic distribution of influenza activity in California was sporadic^#.
Outpatient ILI activity as a percentage of total visits to sentinel providers was 2.4% in week 48 and 2.0% in week 49.
Of the 1007 specimens tested by the Respiratory Laboratory Network (RLN) and sentinel laboratories during week 48, 28 (2.8%) were positive for influenza; of these, two (7.1%) were positive for influenza B and 26 (92.9%) were positive for influenza A. Of the influenza A specimens, one (3.8%) was subtyped as seasonal A (H3), seven (26.9%) were subtyped as 2009 A (H1), and 18 (69.2%) were not subtyped. Of the 1,113 specimens tested during week 49, 58 (5.2%) were positive for influenza; of these, two (3.4%) were positive for influenza B and 56 (96.6%) were positive for influenza A. Of the influenza A specimens, two (3.6%) were subtyped as seasonal A (H3), 23 (41.1%) were subtyped as 2009 A (H1), and 31 (55.4%) 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 5.2% during week 48 and 4.9% during week 49.
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 one report of an influenza-associated death in a person under age 65 during week 49. The person was in the 40-49 year age group and had co-morbid conditions. During the 2013–2014 influenza season, two 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 increased during weeks 48 and 49.
Of the 5,306 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 48, 536 (10.1%) were positive for influenza. During week 49, 830 (13.3%) tests were positive for influenza of 6,219 tests conducted.
The proportion of deaths due to pneumonia and influenza (P&I) was 5.8% in week 48 and 6.2% in week 49, which was below the epidemic threshold for each week.
One influenza-associated pediatric death was reported during week 48 for a death that occurred in week 47.
The proportion of outpatient visits for influenza-like illness (ILI) was 1.9% during week 48 and 2.1% during week 49. In week 49, the ILI percentage exceeded the national baseline of 2.0%.
Two regions reported a proportion of outpatient visits for ILI at or above the region-specific baseline level during week 48 and three regions exceeded their baseline level during week 49. ILI activity was high in two states, moderate in two states, low in New York City and two states, and minimal in 44 states during week 48. ILI activity was high in four states, moderate in no states, low in New York City and five states, and minimal in 41 states during week 49.
During week 48, the geographic spread of influenza activity was reported as regional^ in nine states, local^~ in 13 states, and sporadic^# in 27 states. One state reported no influenza activity. During week 49, the geographic spread of influenza activity was reported as regional^ in 14 states, local^~ in 18 states, and sporadic^# in 16 states. Two states reported no influenza activity. See map for week 49 below.
For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

US Geographic Distribution of Influenza, week 49

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

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

If you have any questions or comments please contact:
Jessica Cunningham, 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%2048%20-%20FINAL%20Report.pdf and http://www.cdph.ca.gov/programs/dcdc/Documents/Week%2049%20-%20FINAL%20Report.pdf. Accessed 12/17/2013.

Centers for Disease Control and Prevention. http://cdc.gov/flu/weekly/ and http://www.cdc.gov/flu/weekly/weeklyarchives2013-2014/weekly48.htm. Accessed 12/17/2013.

Influenza Surveillance Update, Two weeks ending November 23rd

Marin

Influenza-like illness activity: Influenza-like illness activity in Marin County from November 10-23 was minimal. 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 0.23% during week 46 (November 10-16, 2013) and 0.17% in week 47 (November 17-23). 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 46, five (26.3%) of the 19 specimens tested for influenza were positive. All five specimens were influenza A. Of the 37 specimens tested for influenza during week 47, two (5.4%) tested positive for influenza A and none for influenza B. To date during the 2013-2014 influenza season, nine specimens have tested positive for influenza. Although week 46 had a high number and percentage of positive tests, the increase was not sustained in week 47. At this time, the week of higher activity seems to be sporadic and doesn't appear to indicate increased local influenza virus circulation.

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

1. Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, and Novato Community Hospital.

California

During week 46, the geographic distribution of influenza activity in California was sporadic^#.
Outpatient ILI activity as a percentage of total visits to sentinel providers was 1.2% in week 46.
Of the 1,032 specimens tested by the Respiratory Laboratory Network (RLN) and sentinel laboratories during week 46, 15 (1.5%) were positive for influenza A and none for influenza B. Three specimens (20%) was subtyped as seasonal A (H3), four (27%) were subtyped as 2009 A (H1), and eight (53%) 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 4.5% during week 46.
Two specimens from California residents have been strain-typed this season; both 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 46. During the 2013–2014 influenza season, one laboratory-confirmed influenza-associated death in a person under age 65 has been reported in California.
Week 47 data 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 increased slightly during weeks 46 and 47.
Of the 4,457 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 46, 312 (7.0%) were positive for influenza. During week 47, 397 (7.9%) tests were positive for influenza of 4,996 tests conducted.
The proportion of deaths due to pneumonia and influenza (P&I) was 5.8% in both week 46 and week 47, which is below the epidemic threshold for each week.
No influenza-associated pediatric deaths were reported during weeks 46 and 47.
The proportion of outpatient visits for influenza-like illness (ILI) was 1.5% during week 46 and 1.7% during week 47, which are below the national baseline.
One region reported a proportion of outpatient visits for ILI at or above the region-specific baseline level during week 46 and two regions exceeded their baseline level during week 47. ILI activity was high in one state, moderate in two states, low in four states, and minimal in New York City and 43 states during week 46. ILI activity was high in two states, moderate in one state, low in one state, and minimal in New York City and 45 states during week 47. One state had insufficient data to determine ILI activity levels in week 47.
During week 46, the geographic spread of influenza activity was reported as regional^ in four states, local^~ in nine states, and sporadic^# in 34 states. Three states reported no influenza activity. During week 47, the geographic spread of influenza activity was reported as regional^ in six states, local^~ in ten states, and sporadic^# in 32 states. Two states reported no influenza activity. See map for week 47 below.
For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

US Geographic Distribution of Influenza, week 47

^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 re-cent 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, 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%2046%20-%20FINAL%20Report.pdf. Accessed 12/3/2013.

Centers for Disease Control and Prevention. http://cdc.gov/flu/weekly/ and http://www.cdc.gov/flu/weekly/weeklyarchives2013-2014/weekly46.htm. Accessed 12/3/2013.

Influenza Surveillance Update, Two weeks ending November 9th

Marin

Influenza-like illness activity: Influenza-like illness activity in Marin County from October 27 - November 9 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) was 0.43% during week 44 (October 27-November 2, 2013), then increased to 0.68% in week 45 (November 3-9). 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 44, none of the 21 specimens tested for influenza was positive. Of the 18 specimens tested for influenza during week 45, one (5.6%) tested positive for influenza A and none for influenza B. This is the second influenza positive specimen during the 2013-2014 influenza season, but the percentage of positive tests in each week does not yet indicate increased levels of virus circulation.

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

1. Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, and Novato Community Hospital.

California

During weeks 44 and 45, the geographic distribution of influenza activity in California was sporadic^#.
Outpatient ILI activity as a percentage of total visits to sentinel providers was 1.9% in week 44 and 2.1% in week 45.
Of the 705 specimens tested by the Respiratory Laboratory Network (RLN) and sentinel laboratories during week 44, 12 (1.8%) were positive for influenza; of these, two (16.7%) were positive for influenza B and 10 (83.3%) were positive for influenza A. Of the influenza A specimens, one (10%) was subtyped as seasonal A (H3), six (60%) were subtyped as 2009 A (H1), and 3 (30%) were not subtyped. Of the 865 specimens tested by the Respiratory Laboratory Network (RLN) and sentinel laboratories during week 45, 11 (1.3%) were positive for influenza; of these, two (18.2%) were positive for influenza B and nine (81.8%) were positive for influenza A. Of the influenza A specimens, one (11.1%) was subtyped as seasonal A (H3), five (55.6%) were subtyped as 2009 A (H1), and three (33.3%) 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 4.8% during week 44 and 4.1% during week 45.
Two specimens from California residents have been strain-typed this season; both 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 weeks 44 and 45. During the 2013–2014 influenza season, one 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 remained low during week 44 and increased slightly during week 45.
Of the 4,118 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 44, 201 (4.9%) were positive for influenza. During week 45, 231 (5.4%) tests were positive for influenza of 4,257 tests conducted.
The proportion of deaths due to pneumonia and influenza (P&I) was 5.3% in week 44 and 6.1% in week 45, which are both below the epidemic threshold for each week.
Two influenza-associated pediatric deaths were reported during week 45 for the 2013-2014 influenza season.
The proportion of outpatient visits for influenza-like illness (ILI) was 1.4% during week 44 and 1.6% during week 45, which are below the national baseline.
All regions reported a proportion of outpatient visits for ILI below the region-specific baseline level during week 44 and one region exceeded its baseline level during week 45. ILI activity was moderate in one state, low in three states, and minimal in New York City and 46 states during week 44. ILI activity was moderate in two states, low in four states, and minimal in New York City and 44 states during week 45. The District of Columbia had insufficient data to determine ILI activity levels.
During week 44, the geographic spread of influenza activity was reported as regional^ in two states, local^~ in four states, and sporadic^# in the District of Columbia and 34 states. Ten states reported no influenza activity. During week 45, the geographic spread of influenza activity was reported as regional^ in one state, local^~ in eight states, and sporadic^# in the District of Columbia and 35 states. Six states reported no influenza activity. See map for week 45 below.
For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

US Geographic Distribution of Influenza, week 45

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%2045%20-%20FINAL%20Report.pdf and http://www.cdph.ca.gov/programs/dcdc/Documents/Week%2044%20-%20FINAL%20Report.pdf. Accessed 11/15/2013.

Centers for Disease Control and Prevention. http://cdc.gov/flu/weekly/ and http://www.cdc.gov/flu/weekly/weeklyarchives2013-2014/weekly44.htm. Accessed 11/15/2013.

Influenza Surveillance Update, Two weeks ending October 26th

Marin

Influenza-like illness activity:

Influenza-like illness activity in Marin County from October 13-26 was minimal. 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 during week 42 (October 13-19, 2013) showed the percentage of visits associated with influenza-like illness (ILI) decreased to 0.28%, then increased to 0.51% in week 43 (October 20-26). See Figure 1 below.

Marin Influenza-like illness 2011-2013

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 42, none of the 10 specimens tested for influenza was positive. Of the 17 specimens tested for influenza during week 43, one (5.9%) tested positive for influenza A and none for influenza B. This is the first influenza positive specimen during the 2013-2014 influenza season, but the percentage of positive tests during week 43 did not exceed the 10% threshold that indicates increased levels of virus circulation.

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

1. Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, and Novato Community Hospital.

California

During weeks 42 and 43, the geographic distribution of influenza activity in California was sporadic^#.
Outpatient ILI activity as a percentage of total visits to sentinel providers was 1.6% in week 42 then decreased in week 43 to 0.8%.
Of the 707 specimens tested by the Respiratory Laboratory Network (RLN) and sentinel laboratories during week 42, 12 (1.7%) were positive for influenza. All were positive for influenza A, with 3 (25%) subtyped as seasonal A (H3), 3 (25%) subtyped for 2009 A (H1), and 6 not subtyped. Of the 616 specimens tested by the Respiratory Laboratory Network (RLN) and sentinel laboratories during week 43, 14 (2.3%) were positive for influenza. All were positive for influenza A, with 2 (14%) subtyped as seasonal A (H3), 5 (25%) subtyped for 2009 A (H1), and 7 not subtyped.
Kaiser Permanente hospitalization data for northern 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 4.3% during week 42, increasing slightly to 4.4% during week 43.
No specimens from California residents have been strain-typed this season.
California Department of Public Health received one report of an influenza-associated death in a person under age 65 during week 43. This is the first reported death during the 2013–2014 influenza season. The case-patient was in the 50-59 year age group and had co-morbid conditions.
The California Department of Public Health's Influenza Surveillance website contains information about their program.

United States

During weeks 42 and 43, influenza activity remained low in the United States.
Of the 3,513 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 42, 135 (3.8%) were positive for influenza. During week 43, 145 (4.5%) tests were positive for influenza of 3,241 tests conducted.
The proportion of deaths due to pneumonia and influenza (P&I) was 5.8% in week 42 and 5.6% in week 43, which are both below the epidemic threshold for each week.
No influenza-associated pediatric deaths occurring during the 2013-2014 influenza season have been reported.
The proportion of outpatient visits for influenza-like illness (ILI) was 1.2% during both week 42 and week 43, which is below the national baseline.
All regions reported a proportion of outpatient visits for ILI below the region-specific baseline level during weeks 42 and 43. ILI activity was low in two states and minimal in New York City and 48 states during week 42. ILI activity was low in three states and minimal in New York City and 47 states during week 43. The District of Columbia had insufficient data to determine ILI activity levels.
During week 42, the geographic spread of influenza activity was reported as regional in Puerto Rico, local^~ in three states, and sporadic^# in the District of Columbia, Guam, and 28 states. Nineteen states reported no influenza activity. During week 43, the geographic spread of influenza activity was reported as regional in Puerto Rico and one state, local^~ in four states, and sporadic^# in Guam and 30 states. No influenza activity was reported in 15 states. See map for week 43 below.
For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

US Geographic Distribution of Influenza

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%2043%20-%20FINAL%20Report.pdf and http://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%2042%20-%20FINAL%20Report_FINAL.pdf. Accessed 11/6/2013

Centers for Disease Control and Prevention. http://cdc.gov/flu/weekly/ and http://www.cdc.gov/flu/weekly/weeklyarchives2013-2014/weekly42.htm. Accessed 11/6/2013.

Influenza Surveillance Update, Two weeks ending October 12th

This is the first Influenza Surveillance Update of the 2013-2014 influenza season. The report will be prepared bi-weekly until influenza activity begins to increase, then the report will be prepared weekly.

Marin

Influenza-like illness activity:

Influenza-like illness activity in Marin County from September 29 through October 12 was minimal. 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 during week 40 (September 29-October 5, 2013) showed the percentage of visits associated with influenza-like illness (ILI) was 0.34%, increasing to 0.46% in week 41 (October 6-12). See Figure 1 below.
With the addition of Kaiser San Rafael Emergency Department data starting in August 2013 (week 34), influenza-like illness calculations now include all EDs in Marin County. Adding Kaiser data decreased the ILI percentages compared to the percentage for all non-Kaiser facilities.

Marin County influenza-like illness graph

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: No specimens tested positive for influenza during either week 40 or week 41. Six specimens were tested for influenza in week 40 and ten specimens were tested in week 41.

1. Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, and Novato Community Hospital.

California

State-level influenza data aren't yet available for weeks 40-41.
The California Department of Public Health's Influenza Surveillance website contains information about their program.

United States

During weeks 40 and 41, influenza activity was low in the United States.
Of the 3,489 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 40, 163 (4.7%) were positive for influenza. During week 41, 166 (4.7%) tests were positive for influenza of 3,534 tests conducted.
The proportion of deaths due to pneumonia and influenza (P&I) was 5.7% in week 40 and 5.6% in week 41, which are both below the epidemic threshold for each week.
No influenza-associated pediatric deaths occurring during the 2013-2014 influenza season have been reported.
The proportion of outpatient visits for influenza-like illness (ILI) was 1.2% during week 40 and 1.1% during week 41, which are below the national baseline.
All regions reported a proportion of outpatient visits for ILI below the region-specific baseline level during weeks 40 and 41. ILI activity was minimal in New York City and all 50 states during week 40. ILI activity was low in two states and minimal in New York City and 48 states during week 41. The District of Columbia had insufficient data to determine ILI activity levels.
During week 40, the geographic spread of influenza activity was reported as regional in Puerto Rico, local^~ in three states, and sporadic^# in Guam and 26 states. The District of Columbia and 21 states reported no influenza activity. During week 41, the geographic spread of influenza activity was reported as regional in Puerto Rico, local^~ in three states, and sporadic^# in the District of Columbia, Guam, and 22 states. No influenza activity was reported in 22 states and 1 state did not report. See map for week 41 below.
For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

US Influenza Geographic Distribution map

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
Centers for Disease Control and Prevention. http://www.cdc.gov/flu/weekly/pdf/External_F1340.pdf and http://cdc.gov/flu/weekly/. Accessed 10/22/13.

Influenza Surveillance Update, Two weeks ending December 7th

Marin

California

United States

Influenza Surveillance Update, Two weeks ending November 23rd

Marin

California

United States

Influenza Surveillance Update, Two weeks ending November 9th

Marin

California

United States

Influenza Surveillance Update, Two weeks ending October 26th

Marin

California

United States

Influenza Surveillance Update, Two weeks ending October 12th

Marin

California

United States

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