Seasonal influenza morbidity estimates obtained from telephone surveys, 2007

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.

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.

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.

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.