RESUMO
A decade wide (from 1981 to the end of 1993) study on incidences of influenza was carried out in the city of Calcutta, India, by virus isolation and strain identification. Over 3500 patients with acute respiratory infections were examined and 1950 throat swab specimens were inoculated in embryonated chicken eggs. Only 339 haemagglutinating agents were isolated, which comprised 233 strains of influenza A virus. One hundred forty six (62.66%) of these strains were identified as H3N2, eighty one as H1N1 (34.76%), and only two were H2N2 (0.86%) strains of influenza A viruses, as estimated by haemagglutination inhibition test. This observation indicates that H3N2 is the major prevalent strain followed by H1N1 strains of influenza A virus in Calcutta.
