Arbovirus infections of humans in New South Wales. Seroepidemiology of the flavivirus group of togaviruses.

A seroepidemiological study of 16 842 human sera, collected in 1981 and 1982 from all health regions of New South Wales, was carried out using the haemagglutination-inhibition (HI) test and eight Australasian flaviviruses: Murray Valley encephalitis (MVE); Kunjin (KUN); Alfuy (ALF); Stratford (STR); Kokobera (KOK); Edge Hill (EH); Sepik (SEP); and Saumarez Reef (SRE). A limited survey was also carried out with two recently discovered flaviviruses, Gadgets Gully and CSIRO 946. Antibody prevalence rates were low on the coast and tablelands (around 2%-8%), moderate on the western slopes (6%-11%) and high on the western plains (26%-42%). Some centres had higher prevalence rates, Bourke being the highest at 78%. The survey indicated that SEP and SRE viruses are unlikely to infect humans in New South Wales. Similarly, there was no evidence for Gadgets Gully and CSIRO 946 infection of humans. HI antibody prevalence rates were highest to STR, MVE, KUN and ALF in that order, these agents being closely related antigenetically. Reactions to KOK and EH occurred less frequently. Serological tests of greater specificity will be required to identify the flaviviruses that elicit these HI antibodies.