Influenza surveillance in Pune, India, 1978-90.

Continuous surveillance of influenza was carried out in Pune between 1978 and 1990. Most of the cases were identified during investigation of 16 outbreaks of influenza in Pune over this period. The majority of cases were children. Ten of the outbreaks occurred during rainy seasons. A total of 290 isolates consisting of several antigenic variants of influenza type A (H3N2), type A (H1N1), and type B viruses were isolated from throat/nasal swabs that were processed in chick embryos and MDCK cell culture and identified using the haemagglutination inhibition test. These variants circulated every year or in alternate years. Nearly two-thirds of the influenza virus isolates (181 out of 290) were from children aged < 10 years. Seasonal analysis indicated that the highest number of isolates (174) were collected during the rainy months of July, August and September, with the maximum number (93) in July.