County of Marin Health and Human Services

Influenza Surveillance Update, Week ending May 14, 2016

Influenza Surveillance Update Survey

Please take five minutes to respond to our Influenza Surveillance Update Survey:

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


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

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

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

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

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

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


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

Visit for influenza vaccination, testing, and treatment recommendations.


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

United States

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


+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

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

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


California Department of Public Health. Accessed 5/25/2016.

Centers for Disease Control and Prevention. Accessed 5/25/2016.

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