[Studies of influenza in Palermo, 1970-75]

Epidemiological surveillance of influenza was carried out in Palermo betwen 1970 and 1975. Antigenic structure of viral strains A/H3N2 isolated from influenza patients during winter outbreaks was studied in comparison with reference strains circulating in the same periods in other parts of the world. Antigenic drift of hemagglutinin, of neuraminidase, or of both, was observed in Palermo isolates, which were progressively different from Hong Kong/68 strain; 1973 and 1975 isolates were similar to A/England/72 and A/Port Chalmers/73. HI antibodies against Palermo isolates were titered in serum samples obtained from adults living in Palermo. Seronegativity for each strain progressively decreased from 1971 to 1975.