• Janice K Louie, David P Schnurr, Hugo F Guevara, Somayeh Honarmand, Michele Cheung, David Cottam, Elaine Yeh, Lauren Wold, Erica J Boston, Janet Tang, Kate C Cummings, Richard M Donovan, Robert Schechter, Jon Rosenberg, Lawrence J Walter, John A Chapman, Paul R Brenner, Roger P Baxter, and Carol A Glaser.
• Department of Health Services, Viral and Ricksettial Disease Laboratory, California Department of Public Health, 850 Marina Bay Parkway, Richmond, CA 94804, USA. JLouie@dhs.ca.gov
• Am J Prev Med. 2007 Oct 1; 33 (4): 353357353-7.

BackgroundInfluenza surveillance is valuable for monitoring trends in influenza-related morbidity and mortality. Using the 2005-2006 influenza season as an example, this paper describes a comprehensive influenza surveillance program used by the California Department of Public Health (CDPH).MethodsData collected from patients evaluated for acute respiratory illness in a given week were reported and summarized the following week, including (1) electronic hospital pneumonia and influenza admission and antiviral usage records from Kaiser Permanente, (2) sentinel provider influenza-like illness (ILI) reports, (3) severe pediatric influenza case reports (e.g., children either hospitalized in intensive care or expired), (4) school clinic ILI evaluations, and (5) positive influenza test results from a network of academic, hospital, commercial, and public health laboratories and the state CDPH Viral and Rickettsial Disease Laboratory.ResultsInfluenza activity in California in the 2005-2006 season was moderate in severity; all clinical and laboratory markers rose and fell consistently. Extensive laboratory characterization identified the predominant circulating virus strain as A/California/7/2004(H3N2), which was a component of the 2005-2006 influenza vaccine; 96% of samples tested showed adamantane resistance.ConclusionsBy using multiple, complementary surveillance methods coupled with a strong laboratory component, the CDPH has developed a simple, flexible, stable, and widely accepted influenza surveillance system that can monitor trends in statewide influenza activity, ascertain the correlation between circulating strains with vaccine strains, and assist with detection of new strain variants. The methods described can serve as a model for influenza surveillance in other states.

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