Percentage of individuals presenting antibody to A/Asia/57 after an influenza outbreak in a military camp in October 1957

Summary Post-epidemic sera were collected from the recruits in a military camp and the content of antibody to A/Asia/57 was determined in a highly sensitive and specific haemagglutination inhibition test. Of 223 individuals examined 196 (88%) gave serological evidence of having been infected. Of 63 individuals hospitalized with a clinically typical influenza. 2 or 3 were serologically negative. Of 58 individuals with no typical influenza symptoms, antibody was demonstrated in 45 (78%). The most frequent incubation time before clinical symptoms occurred appeared to be 2 days.Supported by a grant from Forsvarets Sanitet.