During 10 years of mosquito collection and processing mosquitoes in the Northern Territory (NT), 231 viruses representing 11 serogroups were isolated from 12 species of mosquitoes (alphaviruses and flaviviruses reported previously). Collection sites were concentrated in the vicinity of major population centres of the Northern Territory during peak vector activity, during potential periods of virus activity (January - July), or in response to the ocurrence of cases of epidemic polyarthritis or Australian encephalitis. Species collected initially were those of human pest species of relatively high numbers, but later collections concentrated on those species from which human disease-causing viruses had previously been isolated in the NT or in other parts of Australia.
Identification of the viral isolates has extended the known distribution of several viruses to include the NT and increased the recognised number of mosquito species from which members of the Bunyavirus (family Bunyaviridae), Orbivirus (family Reoviridae) and Rhabdovirus (family Rhabdoviridae) genera have been isolated. A total of 41 viruses that did not fall into any recognised serogroup were isolated from seven different mosquito species. Preliminary electron microscopy and serologic testing placed the isolates into four groups: (1) bunyavirus-like viruses, seven isolates of which five are serologically identical to each other (2) orbivirus-like viruses, 24 isolates of which two are serologically related to each other (3) a rhabdovirus-like virus unrelated to any recognised Australian rhabdovirus and (4) nine as yet unclassified viruses.