County of Marin Health and Human Services

Influenza Surveillance Update, Two weeks ending October 26th

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Marin

Influenza-like illness activity:

  • Influenza-like illness activity in Marin County from October 13-26 was minimal.  Discharge data from Kaiser San Rafael, Marin General Hospital, and Novato Community Hospital emergency departments and visits to the Sutter Terra Linda Urgent Care Center during week 42 (October 13-19, 2013) showed the percentage of visits associated with influenza-like illness (ILI) decreased to 0.28%, then increased to 0.51% in week 43 (October 20-26).  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 Clinic, 2011-12, 2012-2013, and 2013-2014 Influenza Seasons

Marin Influenza-like illness 2011-2013

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.

Influenza testing1:  During week 42, none of the 10 specimens tested for influenza was positive.  Of the 17 specimens tested for influenza during week 43, one (5.9%) tested positive for influenza A and none for influenza B.  This is the first influenza positive specimen during the 2013-2014 influenza season, but the percentage of positive tests during week 43 did not exceed the 10% threshold that indicates increased levels of virus circulation.

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

1. Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, and Novato Community Hospital.

California

  • During weeks 42 and 43, the geographic distribution of influenza activity in California was sporadic#.
  • Outpatient ILI activity as a percentage of total visits to sentinel providers was 1.6% in week 42 then decreased in week 43 to 0.8%.
  • Of the 707 specimens tested by the Respiratory Laboratory Network (RLN) and sentinel laboratories during week 42, 12 (1.7%) were positive for influenza.  All were positive for influenza A, with 3 (25%) subtyped as seasonal A (H3), 3 (25%) subtyped for 2009 A (H1), and 6 not subtyped.  Of the 616 specimens tested by the Respiratory Laboratory Network (RLN) and sentinel laboratories during week 43, 14 (2.3%) were positive for influenza.  All were positive for influenza A, with 2 (14%) subtyped as seasonal A (H3), 5 (25%) subtyped for 2009 A (H1), and 7 not subtyped.
  • Kaiser Permanente hospitalization data for northern California showed that the percentage of hospitalizations for flu admissions defined as a diagnosis of “flu,” “influenza,” or “pneumonia,” recorded in text fields at time of admission was 4.3% during week 42, increasing slightly to 4.4% during week 43.
  • No specimens from California residents have been strain-typed this season.
  • California Department of Public Health received one report of an influenza-associated death in a person under age 65 during week 43.  This is the first reported death during the 2013–2014 influenza season.  The case-patient was in the 50-59 year age group and had co-morbid conditions.
  • The California Department of Public Health's Influenza Surveillance website contains information about their program.

United States

  • During weeks 42 and 43, influenza activity remained low in the United States.
  • Of the 3,513 specimens tested by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories and reported to CDC/Influenza Division during week 42, 135 (3.8%) were positive for influenza.  During week 43, 145 (4.5%) tests were positive for influenza of 3,241 tests conducted.
  • The proportion of deaths due to pneumonia and influenza (P&I) was 5.8% in week 42 and 5.6% in week 43, which are both below the epidemic threshold for each week.
  • No influenza-associated pediatric deaths occurring during the 2013-2014 influenza season have been reported.
  • The proportion of outpatient visits for influenza-like illness (ILI) was 1.2% during both week 42 and week 43, which is below the national baseline.
  • All regions reported a proportion of outpatient visits for ILI below the region-specific baseline level during weeks 42 and 43.  ILI activity was low in two states and minimal in New York City and 48 states during week 42.  ILI activity was low in three states and minimal in New York City and 47 states during week 43.  The District of Columbia had insufficient data to determine ILI activity levels.
  • During week 42, the geographic spread of influenza activity was reported as regional in Puerto Rico, local~ in three states, and sporadic# in the District of Columbia, Guam, and 28 states.  Nineteen states reported no influenza activity.  During week 43, the geographic spread of influenza activity was reported as regional in Puerto Rico and one state, local~ in four states, and sporadic# in Guam and 30 states.  No influenza activity was reported in 15 states. See map for week 43 below.
  • For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

US Geographic Distribution of Influenza

^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 re-cent 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:
Jessica Cunningham, MPH
Epidemiologist
(415) 473-7346
JCunningham@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

California Department of Public Health.  http://www.cdph.ca.gov/programs/dcdc/Documents/Week%2043%20-%20FINAL%20Report.pdf and http://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%2042%20-%20FINAL%20Report_FINAL.pdf. Accessed 11/6/2013

Centers for Disease Control and Prevention.  http://cdc.gov/flu/weekly/ and http://www.cdc.gov/flu/weekly/weeklyarchives2013-2014/weekly42.htm. Accessed 11/6/2013.

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