A serological investigation into the epidemiology of influenza with particular reference to sporadic cases

Abstract

An investigation has been described in which the complement fixing antibody titres of selected groups of the population have been correlated with the occurrence of epidemic and sporadic influenza and of other cases of respiratory disease which it was thought might be due to the virus of epidemic influenza.During two non-epidemic seasons the influenza virus could not be isolated from cases of apparent influenza neither could any serological evidence be obtained of the existence of any form of respiratory disease caused by the virus.With rare exceptions individual antibody titres either remain constant, or if they are high show a tendency to fall during non-epidemic times, and periodic investigations of sample groups each consisting of several hundred sera show a wave-like fluctuation in the titres of the population consisting of a sudden rise followed by a gradual fall, the former being an accompaniment of an epidemic. Such a wave-like fluctuation appears to be an indication of variations in the immunity of the population, and to be responsible in part, at least, for the occurrence of large influenza epidemics.I wish to acknowledge the help received from all who took part in this investigation, and in particular to thank the students of the University Halls of Residence in Manchester, the numerous doctors who helped by supplying particulars of cases of influenza and to Dr R. W. Fairbrother who has given advice and maintained a constant interest throughout the investigation.