ARTHROPOD‐BORNE VIRUSES IN AUSTRALIA, 1973‐1976

Summary The period 1973‐76 saw additions to knowledge of Australian arboviruses in several directions. A large epidemic of Murray Valley encephalitis (MVE) allowed evaluation of serological diagnostic techniques not available in previous major outbreaks, and also added to knowledge of clinical features and epidemiology. Its wide geographical distribution, with cases recognized for the first time in central Australia, suburhan Adelaide and east central Queensland, possibly associated with what has been described as “the most extraordinary set of weather conditions to affect Australia in this century”, triggered new consideration of epidemic prediction and vector control. The recognition of regular summer‐autumn occurrence of epidemic polyarthritis in southern Australia suggested the possibility of year‐round survival of Ross River virus, and perhaps of other togaviruses, in that area. Further evidence was obtained for previous suggestions that Kunjin virus might cause febrile disease of man. Bovine ephemeral fever was repeatedly epizootic and its epidemiology became a major focus of investigation, with accent on possibilities of control by vaccination. Important progress was made in Japan and then in Australia in linking Akabane virus with a disease of domestic animals. The continuation of field programmes in Queensland and Western Australia, and the commencement of new ones in Northern Territory, the Murray Valley of Victoria and elsewhere, led to the discovery of “new” viruses and extended the known host and geographic range of other viruses, adding complexity to the Australian arbovirus pattern. An ambitious programme of serological surveillance of virus infection in sentinel cattle herds covered a wide area of Australia and New Guinea and produced important results which could well be supplemented in other hosts. Progress in this period does not contradict the previous suggestion that complete elucidation of the epidemiology of arboviruses in Australia is a distant goal within the limits of current techniques, but it does suggest that collaboration between units and between disciplines can provide steady and useful progress.