MEDICAL PRACTICE-BASED INFLUENZA SURVEILLANCE - VIRAL PREVALENCE AND ASSESSMENT OF MORBIDITY

Regular surveillance of influenza virus activity and associated illnes s is necessary to monitor changes in circulating strains, As part of a demonstration project, medical practices in a seven-county area in so uthern lower Michigan were recruited as sentinel surveillance sites. T he practices were asked to collect specimens for virus isolation and/o r data on age-specific frequency of respiratory illnesses that met a c ase definition. Data were used to establish periods of influenza virus activity for vaccine effectiveness determinations, Over three study p eriods, 1989-1992, there were documented outbreaks of influenza type A (H3N2), type A(H1N1), and type B. The incidence of influenza-like illn ess increased during these outbreaks, with variation in age-specific f requency from year to year. Recovery of virus was not affected during the winter season by long delays in specimen receipt by the laboratory . Results indicated that medical practices can be successfully recruit ed as surveillance sites to provide information on the timing, etiolog y, and intensity of acute respiratory illness.