Last mentioned on the blog in March of 2015, Ross River virus (RRV) has returned in force to Victoria, a state in Australia. Since the beginning of the year, there have been 1012 cases in the state, with over 150 found to be infected in the last week. These are record numbers in infection, dwarfing even 2010, when the outbreak was notable due to widespread flooding that provided breeding grounds for the mosquito vectors that transmit the virus. Similarly, the reason this year has been such a large year for Ross River virus is due to extended rain and a number of warm, summer days that have been a boon to mosquito reproduction.
In order to combat the mosquito vectors, the Victorian Health Department has employed over $4 million dollars in emergency funds to eliminate standing water and spray for mosquitoes, among other activities. They are also encouraging many common mosquito bite prevention techniques: putting screens on windows, wearing long sleeves and pants, dumping out standing water, and using repellent.
There are 40 or more species of mosquitoes that may transmit this alphavirus (of the Togaviridae family) with those of the Aedes and Culex genera being the most prominent. In addition to having a wide range of vectors, RRV has a number of animal reservoirs, including wallabies, kangaroos, horses, and humans. The latter of which has likely been involved in outbreaks where few animals are found, such as in urban centers.