Abstract
Distribution of antibodies against swine influenza viruses, A/New Jersey/8/76 and A/Wisconsin/15/30, was examined in sera collected after the 1975-76 pandemic of Hong Kong influenza virus in Japan. Although persons from all age groups were examined, only those born before 1924-25 exhibited a characteristic serological involve-ment with the virus. This finding was believed to indicate that swine influenza virus had died out in Japan during 1930-31 and had never reappeared up to this time (1976). The hemagglutination-inhibition (HI) tests with sera from persons aged 44 or more showed that the hemagglutinins of the “old” and “new” swine influenza viruses were identical. However, the results with sera from persons recently vaccinated with the “new” strain showed some antigenic differences. The same study conducted with swine sera suggested that Japanese pigs had been exposed to the Hong Kong-like influenza virus, but not to swine influenza virus.
