Influenza A: infection and reinfection.

Twenty-nine boys in a boarding school were present during a large outbreak of influenza A H1N1 in 1978 when 27 were infected, 21 with clinical influenza. These boys were bled annually and were still in school when another outbreak of influenza A H1N1 occurred in 1983. Twenty-three of them were reinfected but only nine had symptoms. These results are compared with the experience of a similar group of boys in the early years of the influenza A H3N2 era.