Influenza-like illness activity: Influenza-like illness activity in Marin County from November 24-December 7 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) increased to 0.84% during week 48 (November 24-30, 2013) and decreased to 0.56% in week 49 (December 1-7). 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
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 48, two (7.4%) of the 27 specimens tested for influenza were positive. Of the 39 specimens tested for influenza during week 49, six (15.4%) tested positive. All positive tests in both weeks were influenza A viruses. To date during the 2013-2014 influenza season, 17 specimens have tested positive for influenza. The elevated percentage during week 49 and preliminary data showing similar percentages for week 50 suggest that influenza virus may be circulating locally.
1. Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, and Novato Community Hospital.
Visit MarinFlu.org for influenza vaccination, testing, and treatment recommendations.
- During weeks 48 and 49, the geographic distribution of influenza activity in California was sporadic#.
- Outpatient ILI activity as a percentage of total visits to sentinel providers was 2.4% in week 48 and 2.0% in week 49.
- Of the 1007 specimens tested by the Respiratory Laboratory Network (RLN) and sentinel laboratories during week 48, 28 (2.8%) were positive for influenza; of these, two (7.1%) were positive for influenza B and 26 (92.9%) were positive for influenza A. Of the influenza A specimens, one (3.8%) was subtyped as seasonal A (H3), seven (26.9%) were subtyped as 2009 A (H1), and 18 (69.2%) were not subtyped. Of the 1,113 specimens tested during week 49, 58 (5.2%) were positive for influenza; of these, two (3.4%) were positive for influenza B and 56 (96.6%) were positive for influenza A. Of the influenza A specimens, two (3.6%) were subtyped as seasonal A (H3), 23 (41.1%) were subtyped as 2009 A (H1), and 31 (55.4%) 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 5.2% during week 48 and 4.9% during week 49.
- Ten specimens from California residents have been strain-typed this season; all matched components of the 2013-2014 influenza vaccine.
- California Department of Public Health received one report of an influenza-associated death in a person under age 65 during week 49. The person was in the 40-49 year age group and had co-morbid conditions. During the 2013–2014 influenza season, two 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.
- Influenza activity in the United States increased during weeks 48 and 49.
- Of the 5,306 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 48, 536 (10.1%) were positive for influenza. During week 49, 830 (13.3%) tests were positive for influenza of 6,219 tests conducted.
- The proportion of deaths due to pneumonia and influenza (P&I) was 5.8% in week 48 and 6.2% in week 49, which was below the epidemic threshold for each week.
- One influenza-associated pediatric death was reported during week 48 for a death that occurred in week 47.
- The proportion of outpatient visits for influenza-like illness (ILI) was 1.9% during week 48 and 2.1% during week 49. In week 49, the ILI percentage exceeded the national baseline of 2.0%.
- Two regions reported a proportion of outpatient visits for ILI at or above the region-specific baseline level during week 48 and three regions exceeded their baseline level during week 49. ILI activity was high in two states, moderate in two states, low in New York City and two states, and minimal in 44 states during week 48. ILI activity was high in four states, moderate in no states, low in New York City and five states, and minimal in 41 states during week 49.
- During week 48, the geographic spread of influenza activity was reported as regional^ in nine states, local~ in 13 states, and sporadic# in 27 states. One state reported no influenza activity. During week 49, the geographic spread of influenza activity was reported as regional^ in 14 states, local~ in 18 states, and sporadic# in 16 states. Two states reported no influenza activity. See map for week 49 below.
- For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.
^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:
Jessica Cunningham, MPH
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. http://www.cdph.ca.gov/programs/dcdc/Documents/Week%2048%20-%20FINAL%20Report.pdf and http://www.cdph.ca.gov/programs/dcdc/Documents/Week%2049%20-%20FINAL%20Report.pdf. Accessed 12/17/2013.
Centers for Disease Control and Prevention. http://cdc.gov/flu/weekly/ and http://www.cdc.gov/flu/weekly/weeklyarchives2013-2014/weekly48.htm. Accessed 12/17/2013.