Ecology and epidemiology of Ross River virus in Western Australia

[Truncated] Ross River (RR) virus is a mosquito-borne alphavirus that causes a debilitating disease in humans known as epidemic polyarthritis or RR virus disease. It is now regarded as the most common cause of arboviral illness in humans in Australia. Illness due to infection with RR virus in Western Australia (WA) was first recognised as early as 1956. The disease was made notifiable by the Health Department of Western Australia in 1985 but no thorough analysis of the seasonal and regional incidence of RR virus disease in WA has been carried out. Similarly, very little was known about mosquito vectors and vertebrate hosts of the virus in WA, except for that which could be extrapolated from studies in eastern Australia. It seemed likely that the incidence of disease, the vectors and hosts would vary from one region of WA to another given the considerable variation in climate and geography experienced throughout the state. Several other questions about the ecology of RR virus have also remained unanswered. The means by which the virus survives between outbreaks of human disease or is reintroduced to non-endemic regions is not known. There is evidence for the existence of different genotypes of the virus in geographically disparate regions of eastern Australia but it is not known whether this is also the case in WA. Similarly, it is not known whether certain genotypes are more likely to cause outbreaks of human disease.