Ross River virus is a mosquito-borne alphavirus endemic in Australia and some South Pacific islands.

Infection in Australia can occur year round. In the south, infection is most common in the summer and fall. In the north, infection is most common in the wet season.

Symptoms are similar to those caused by other alphaviruses. After an incubation period of 3-9 days (but as long as 21 days), patients present with fever, general malaise, and a nonspecific rash. Arthralgias or symmetric polyarthritis are very common. Symptoms usually last about 10 days, but a subset of patients report fatigue and arthralgias for months. The symptoms are clinically indistinguishable from Barmah Forest virus (the other alphavirus endemic in Australia), though illness from Barmah Forest virus tends to be milder.