ABSTRACT
Numerous outbreaks of epidemic polyarthritis were recognized throughout eastern Australia after 1928. Ross River (RR) virus is a member of the Getah serogroup of alphaviruses. RR virus has an extremely broad host range, but only produces clinical infection in humans, laboratory mice, and possibly horses. On the basis of virulence for suckling mice, there is extensive variation between clones of virus from within a single isolate, between isolates from one geographic region, and between isolates from different geographic regions. RR virus has been isolated consistently from mosquitoes following inoculation into suckling mice. RR virus is endemic in Australia and probably also in parts of Papua New Guinea. In view of the endemicity of RR virus in Australia, its numerous vectors, and the relatively cumbersome virus isolation methods used, surveillance based on vectors is considered impracticable. RR virus readily crosses the placenta of mice, but in utero infection occurs at a very low rate in humans.
