Murray Valley encephalitis virus
Murray Valley encephalitis (MVE) occurs primarily in southeastern Australia, with cases appearing occasionally in other parts of the country and in Papua New Guinea. Febrile disease leads to encephalitis and, in severe cases, death. Neurologic sequelae are common in survivors. Children are predominantly affected. Large water birds are the main vertebrate amplifying hosts, but mammals are also reservoirs. The virus is transmitted mainly by Culex annuliros-tris mosquitoes. It is maintained in northern Australia and New Guinea and is believed to be introduced into southern Australia in years of high rainfall. MVE virus is a flavivirus of the Togaviridae and is closely related to Japanese encephalitis. RNA sequencing indicates that the Australian strains of MVE virus are similar to, but different from Papua New Guinea isolates. Like JE, MVE diagnosis depends on virus isolation and serological testing. No vaccine is available. Control is achieved through application of larvicides.
Ross River (RR) virus has caused annual epidemics of febrile disease with polyarthritis and rash in tropical and temperate eastern Australia. Within the past two decades, RR virus has spread through several Pacific islands in epidemic form and appears to have become endemic in New Caledonia. Convalescence can be long. RR virus is an alphavirus of the Togaviridae family. The enzootic maintenance cycles of RR virus in Australia are not well defined, but wild and domestic mammals appear to be the reservoir hosts, and the principal mosquito vectors are salt marsh Aedes spp. and freshwater Culex spp. In the Pacific Islands, the virus was probably transmitted from person to person by Aedes mosquitoes.
Kunjin virus has caused scattered cases of fever, myalgia and polyarthralgia across Australia and in clusters in central Queensland and northern Western Australia. Kunjin virus is a flavivirus of the Togaviridae, and is related to WN and MVE viruses. The virus is believed to be maintained in wild bird-Cx annulirostris transmission cycles similar to MVE virus.
Burmah Forest virus causes subclinical and clinical infections in humans, including fever, myalgia, poly-arthalgia and rash. It is an alphavirus in the Togaviridae. The virus appears to be endemic in eastern Australia, and its mosquito vectors and vertebrate hosts have not been established.
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