Mixed respiratory viral infections during influenza A epidemics

Mixed respiratory viral infections occurring in the course of 8 influenza A epidemics in the Estonian SSR between 1969 and 1978 were investigated. A total of 1638 patients were followed up. The IF method, serological test CFR and HIR and isolation of the virus on tissue cultures and chick embryos were used. Mixed infections were found in 0-77.7% of laboratory-confirmed cases, depending on the epidemic. A combination of influenza A + parainfluenza was observed most frequently during the influenza epidemics in 1971-1977 and a combination of influenza A + influenza B during the 1977-1978 epidemic.