[Complement fixation, hemagglutination inhibition and neuraminidase inhibition reactions in the seroepidemiologic evaluation of an influenza A epidemic].

Complement-fixing (CF), hemagglutination-inhibiting (HI) and neuraminidase-inhibiting (NI) antibodies in respect of type A influenza virus were titrated on 2080 serum specimens. The sera were collected between December 1974 and May 1975 for the open population of Rome, in groups of an average of 300 samples per month. Influenza type A strains, related to the Port Chalmers variant, were isolated in Rome in January and February 1975, during that time a significant increase of antibody titers and of serum positivity was detected. The increase of positive response for influenza type A antigen was of 21%, 17% and 8% for FC, HI and NI reactions, respectively. The NI reaction proved to be less responsive that the CF and HI reactions for the purposes of sero-epidemiological evaluation of the influenza epidemic.