County of Marin Health and Human Services

Influenza Surveillance Update, Week ending December 31, 2016

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

Clinical Updates

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


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

Influenza testing1 

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

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

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

Visit for influenza vaccination, testing, and treatment recommendations.


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

United States

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

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

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

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 1/5/2017.

Centers for Disease Control and Prevention. Accessed 1/5/2017.

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