County of Marin Health and Human Services

Influenza Surveillance Update - Week Ending March 23, 2019


Influenza-like illness activity has increased in Marin.  Positive tests have remained elevated throughout 2019.

Influenza-like illness activity 

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) has increased to elevated levels in March and are above expected levels for this time of year.  

Influenza testing

During week 12 (March 17-23), 30 (20.8%) of the 144 specimens tested for influenza were positive.  Of the positive specimens from week 12, 28 (93.3%) were influenza A and 2 (6.7%) were influenza B. During this influenza season through March 123, 394 specimens have tested positive for influenza.  See Figure 1 below. 

Figure 1. Influenza Tests in Marin County, 2018-2019 Influenza Season



Figure : Proportion of Visits due to Influenza-Like Illness (ILI):  Marin County Kaisers, MGH, and NCH Emergency Departments, 2016-2017, 2017-2018, and 2018-2019 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.

Visit for influenza vaccination, testing, and treatment recommendations.


The geographic spread of influenza activity in California is widespread during the week 11 (March 10-16).
Outpatient influenza-like illness and hospitalizations were above expected levels.
Visit the California Department of Public Health’s influenza website for more information.  

United States

Influenza activity remained elevated nationally during week 11 (March 10-16).
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:
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 3/27/19.

Centers for Disease Control and Prevention. Accessed 3/27/19.

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