County of Marin Health and Human Services

Influenza Surveillance Update, Two weeks ending November 9th

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Marin

Influenza-like illness activity:  Influenza-like illness activity in Marin County from October 27 - November 9 was low.  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 showed the percentage of visits associated with influenza-like illness (ILI) was 0.43% during week 44 (October 27-November 2, 2013), then increased to 0.68% in week 45 (November 3-9).  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 SeasonsMarin 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 44, none of the 21 specimens tested for influenza was positive.  Of the 18 specimens tested for influenza during week 45, one (5.6%) tested positive for influenza A and none for influenza B.  This is the second influenza positive specimen during the 2013-2014 influenza season, but the percentage of positive tests in each week does not yet indicate 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 44 and 45, the geographic distribution of influenza activity in California was sporadic#.
  • Outpatient ILI activity as a percentage of total visits to sentinel providers was 1.9% in week 44 and 2.1% in week 45.
  • Of the 705 specimens tested by the Respiratory Laboratory Network (RLN) and sentinel laboratories during week 44, 12 (1.8%) were positive for influenza; of these, two (16.7%) were positive for influenza B and 10 (83.3%) were positive for influenza A.  Of the influenza A specimens, one (10%) was subtyped as seasonal A (H3), six (60%) were subtyped as 2009 A (H1), and 3 (30%) were not subtyped.  Of the 865 specimens tested by the Respiratory Laboratory Network (RLN) and sentinel laboratories during week 45, 11 (1.3%) were positive for influenza; of these, two (18.2%) were positive for influenza B and nine (81.8%) were positive for influenza A.  Of the influenza A specimens, one (11.1%) was subtyped as seasonal A (H3), five (55.6%) were subtyped as 2009 A (H1), and three (33.3%) were not subtyped.
  • Kaiser Permanente hospitalization data for northern and southern 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 4.8% during week 44 and 4.1% during week 45.
  • Two specimens from California residents have been strain-typed this season; both matched components of the 2013-2014 influenza vaccine.
  • California Department of Public Health received no reports of influenza-associated deaths in persons under age 65 during weeks 44 and 45.  During the 2013–2014 influenza season, one laboratory-confirmed influenza-associated death in a person under age 65 has been reported in California. 
  • The California Department of Public Health's Influenza Surveillance website contains information about their program.

United States

  • Influenza activity in the United States remained low during week 44 and increased slightly during week 45.
  • Of the 4,118 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 44, 201 (4.9%) were positive for influenza.  During week 45, 231 (5.4%) tests were positive for influenza of 4,257 tests conducted.
  • The proportion of deaths due to pneumonia and influenza (P&I) was 5.3% in week 44 and 6.1% in week 45, which are both below the epidemic threshold for each week.
  • Two influenza-associated pediatric deaths were reported during week 45 for the 2013-2014 influenza season.
  • The proportion of outpatient visits for influenza-like illness (ILI) was 1.4% during week 44 and 1.6% during week 45, which are below the national baseline.
  • All regions reported a proportion of outpatient visits for ILI below the region-specific baseline level during week 44 and one region exceeded its baseline level during week 45.  ILI activity was moderate in one state, low in three states, and minimal in New York City and 46 states during week 44.  ILI activity was moderate in two states, low in four states, and minimal in New York City and 44 states during week 45.  The District of Columbia had insufficient data to determine ILI activity levels.
  • During week 44, the geographic spread of influenza activity was reported as regional^ in two states, local~ in four states, and sporadic# in the District of Columbia and 34 states.  Ten states reported no influenza activity.  During week 45, the geographic spread of influenza activity was reported as regional^ in one state, local~ in eight states, and sporadic# in the District of Columbia and 35 states.  Six states reported no influenza activity. See map for week 45 below.
  • For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.

US Geographic Distribution of Influenza, week 45

^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%2045%20-%20FINAL%20Report.pdf and http://www.cdph.ca.gov/programs/dcdc/Documents/Week%2044%20-%20FINAL%20Report.pdf. Accessed 11/15/2013.

Centers for Disease Control and Prevention.  http://cdc.gov/flu/weekly/ and http://www.cdc.gov/flu/weekly/weeklyarchives2013-2014/weekly44.htm. Accessed 11/15/2013.

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