Contrasting Seroepidemiology of Australia Antigen and Arbovirus Antibodies in New Guinea1

Serologic surveys in adults of the Bismarck Range and children and adults in the Sepik District of New Guinea were undertaken to provide basic information on the epidemiology of Australia (Au) antigen in a tropical environment. The Bismarck Range population was sampled once only, in 1964, but the majority of the Sepik study population was surveyed longitudinally from March 1963 to May 1964 (15 months). The Au antigen status of the population was contrasted with the antibody status to several arboviruses of Groups A and B. Whereas the incidence of arbovirus antibodies was strongly correlated with that of mosquito activity and inversely related to altitude, the frequency of Au antigen was not related to either of these factors. Thus, transmission of Au antigen by mosquito vectors could not be implicated in New Guinea. The overall incidence of Au antigen was 4.1% in the Bismarck Range population and 2.6% in the Sepik population. Au antibody was not detected in any of the natives. Each of 24 antigen positive children surveyed longitudinally maintained their antigenemia for the duration of the survey, as did 4 children who acquired the antigen during the survey. There was no statistically significant difference between the frequency of the antigen in male and female natives. The incidence of arbovirus antibodies in the population increased cumulatively with age, but that of Au antigen did not increase significantly with age. Whereas the proportion of the susceptible population acquiring arbovirus antibodies during the study was similar in all age groups, all the children acquiring Au antigen were in the group aged 2 years or less at the commencement of the survey. Thus, both cross-sectional and longitudinal surveys suggested that although arbovirus infection occurred with equal facility in all age groups, persistent carriage of Au antigen was most likely to occur if individuals were infected with the Au antigen-associated virus during the first two or three years of life.