County of Marin Health and Human Services

Influenza Surveillance Update - Week Ending December 28, 2019


Local influenza activity continues to increase in Marin County with a spike in activity seen at the end of 2019. Current data suggests that the 2019-2020 flu season will be a more severe season. It is not too late to get the flu vaccine if you haven't already. You can find out where to receive the flu vaccine here.

Influenza-like Illness Activity

Influenza-like illness activity in Marin County has remain elevated levels since early November, with a larger spike in activity seen starting in mid-December. Discharge data from Kaiser San Rafael, MarinHealth, and Novato Community Hospital emergency departments showed the percentage of visits associated with influenza-like illness (ILI) was 11.6% during week 52 (Dec. 22-28). See Figure 1 below.

Figure 1. Proportion of Visits due to Influenza-Like Illness (ILI):  Kaiser San Rafael, MarinHealth Medical Center, and Novato Community Hospital Emergency Departments, 2017-2018, 2018-2019, and 2019-2020 Influenza Seasons


Influenza testing: During week 52 (Dec. 22-28), 27 (20.3%) of the 133 specimens tested for influenza were positive. During this influenza season through December 28, 168 specimens have tested positive for influenza. See Figure 2 below. 

Figure 2. Influenza Tests in Marin County, 2019-2020 Influenza Season


Influenza Related Deaths: There have been two influenza-related deaths of older adults (>65 years old) in Marin County during the 2019-2020 flu season.

Note: Marin County now includes number of influenza-related deaths in our influenza communications. This does not indicate an increase in deaths compared to previous flu seasons, but a change in reporting procedures.


The geographic spread of influenza activity in California was widespread during week 52 (Dec. 22-28).
Outpatient influenza-like illness and hospitalizations were above expected levels.
Visit the California Department of Public Health’s influenza website here for more information.

United States

National influenza activity was high and continued to increase during week 52 (Dec. 22-28).
For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website here.

If you have any questions or comments please contact:
Lisa Santora, MD
Deputy Public Health Officer
(415) 473-4163

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 1/9/20.

Centers for Disease Control and Prevention. Accessed 1/9/20.

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