County of Marin Health and Human Services

Influenza Surveillance Update, Two weeks ending December 26, 2016

Marin

During weeks 50 (December 13-19) and 51 (December 20-26), influenza-like illness activity in Marin increased slightly from previous weeks (Figure 1). However, the percent of positive influenza tests decreased during weeks 50 and 51 in comparison to weeks 48 and 49 (Figure 2).

Influenza-like illness activity

Influenza-like illness activity in Marin County was low during weeks 50 (December 13-19) and 51 (December 20-26). 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) increased slightly to 9.2% during week 50 and 10.0% during week 51. 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 SeasonsInfluenza-like illness, Marin County, 2012-2015

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 were no positive tests during weeks 50 and 51 out of 29 and 27 tests conducted, respectively. During this influenza season through December 26, 16 specimens have tested positive for influenza. See Figure 2 below.

Figure 2. Influenza Tests in Marin County, 2015-2016 Influenza Season
Influenza Tests in Marin County, 2014-2015

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

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

California

  • There has not been a report released on state-wide influenza activity for weeks 50 and 51.
  • Visit the California Department of Public Health's influenza surveillance website for more information on influenza activity during previous weeks.

United States

  • Influenza activity increased slightly during weeks 50 and 51 compared to previous weeks.
  • The proportion of outpatient visits for influenza-like illness (ILI) was 2.2% during week 50 and 2.6% during week 51, which are both above 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, 2.9% (372 of 12,890 specimens tested) were positive for influenza during week 50 and 2.5% (282 of 11,448 specimens tested) were positive for influenza during week 51.
  • During week 50, the geographic spread of influenza activity was reported as regional* in five states, local^ in 14 states, and sporadic~ in 27 states and the District of Columbia. No activity was reported in four states. During week 51, the geographic spread of influenza activity was reported as widespread+ in one state, regional* in five states, local^ in 12 states, and sporadic~ in 29 states. No influenza activity was reported by three states and the District of Columbia. See map below for week 51.
  • For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

usmap49.jpg

+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 http://www.google.org/flutrends/

If you have any questions or comments please contact:
Haylea Hannah, MSPH
Epidemiology Fellow
(415) 473-6020
HHannah@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. https://www.cdc.gov/flu/weekly/. Accessed 1/5/2016.

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