Seasonal influenza morbidity estimates obtained from telephone surveys, 2007

Objectives: We assessed telephone surveys as a novel surveillance method, comparing data obtained by telephone with existing national influenza surveillance systems, and evaluated the utility of telephone surveys. Methods: We used the 2007 Behavioral Risk Factor Surveillance System (BRFSS) and the 2007 National Immunization Survey-Adult (NIS-Adult) to estimate the incidence of influenza-like illness (ILI), medically attended ILI, provider-diagnosed influenza, influenza testing, and treatment of influenza with antiviral medications during the 2006-2007 influenza season. Results: With the January-May BRFSS, among persons aged 18 years and older, the cumulative incidence of seasonal ILI and provider-diagnosed influenza was 37.9 and 5.7 adults per 100 persons, respectively. Monthly medically attended ILI and provider-diagnosed influenza among adults were temporally associated with influenza activity, as documented by national surveillance. With the NIS-Adult survey data, estimated provider-diagnosed influenza, influenza testing, and antiviral treatment were 2.8%, 1.4%, and 0.6%, respectively. Conclusions: Our telephone interview-based estimates of influenza morbidity were consistent with those from national influenza surveillance systems. Telephone surveys may provide an alternative method by which population-based influenza morbidity information can be gathered.