During week 48 (November 29-December 5) and week 49 (December 6-12), influenza-like illness remained minimal in Marin. The number of tests conducted has remained elevated since early November, however, there are still relatively few positive tests. The percent positive has not increased from prior weeks, which should serve as a reminder to all providers that it is not too late to discuss and offer immunization to our unvaccinated patient population.
Influenza-like illness activity
Influenza-like illness activity in Marin County was minimal during weeks 48 (November 29-December 5) and 49 (December 6-12). 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 9.1% during week 48 and 8.8% during week 49. 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 Seasons
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.
During week 48, 1 (3.4%) of the 29 specimens tested for influenza was positive.2 The positive specimen from week 48 was influenza B. During week 49, 2 (5.4%) of the 37 specimens tested for influenza were positive. All positive specimens from week 49 were influenza A. During this influenza season through December 12, 16 specimens have tested positive for influenza. See Figure 2 below.
Figure 2. Influenza Tests in Marin County, 2015-2016 Influenza Season
1. Laboratory results reported by Kaiser-Novato, Kaiser-San Rafael, Marin General Hospital, Novato Community Hospital, and Sutter Terra Linda Urgent Care.
2. All data have not been received for week 48. Data are preliminary and subject to change.
Visit MarinFlu.org for influenza vaccination, testing, and treatment recommendations.
- Influenza activity in California remains minimal and sporadically~ distributed.
- Outpatient ILI activity as a percentage of total visits to sentinel providers remained the same for weeks 48 and 49 at 1.9%.
- Of the specimens tested by the Respiratory Laboratory Network and Sentinel Laboratories, 2.5% (50 of 2,014 specimens tested) were positive for influenza during week 48 and 1.7% (23 of 1,344 specimens tested) were positive for influenza during week 49.
- Visit the California Department of Public Health's influenza surveillance website for more information.
- Influenza activity increased slightly from previous weeks but remained low overall.
- The proportion of outpatient visits for influenza-like illness (ILI) was 1.8% during week 48 and 1.9% during week 49.
- 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, 1.6% (185 of 11,509 specimens tested) were positive for influenza during week 48 and 1.7% (208 of 12,525 specimens tested) were positive for influenza during week 49.
- During week 48, the geographic spread of influenza activity was reported as local^ in 10 states and sporadic~ in 37 states. No activity was reported in the District of Columbia and three states. During week 49, the geographic spread of influenza activity was reported as regional* in two states, local^ in 12 states, and sporadic~ in the District of Columbia and 33 states. See map below for week 49.
- For additional national influenza data, visit the Center for Disease Control and Prevention's influenza surveillance website.
+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
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/HealthInfo/discond/Documents/Week%2049%20-%20FINAL%20Report.pdf and http://www.cdph.ca.gov/HealthInfo/discond/Documents/Week%2048%20-%20FINAL%20Report.pdf. Accessed 12/18/2015.
Centers for Disease Control and Prevention. https://www.cdc.gov/flu/weekly/. Accessed 12/18/2015.