West Nile virus - is it a serious threat to Australians?
West Nile virus - is it a serious threat to Australians?
West Nile virus - responsible for widespread disease and deaths in the United States in recent years - has the potential to enter Australia either through slow spread through Asia, or through an infected mosquito or traveler carried on an aircraft. However, it may not be as serious a threat locally as it has been in the US.
According to three prominent Australian experts on molecular and microbiological sciences - Professor John Mackenzie and Dr Roy Hall (University of Queensland, Brisbane) and Dr David Smith (The Western Australian Centre for Pathology and Medical Research, Perth) - the long-time presence in Australia of Kunjin virus may protect Australians from the worst effects of West Nile virus.
Their views are contained in an editorial in the latest edition of the Medical Journal of Australia.
West Nile virus is spread by mosquitoes and birds. In August 1999, it caused an outbreak in New York. By November 2002, it had spread to 43 US states, with 3735 reported clinical cases and 215 deaths, mostly of older people.
Closely related to Japanese encephalitis virus, West Nile virus causes symptoms that include high fever, chills, malaise, headache, backache, joint pain, muscle pain, retro-orbital pain (behind the eye), and, more recently recognised, severe neurological illness, such as encephalitis and meningitis.
West Nile virus is almost identical genetically and immunologically to Kunjin virus, which is the most common flavivirus in Australia, occurring widely across northern Australia.
Unlike West Nile virus, Kunjin virus usually causes no symptoms. It has been in our ecological system for many years without any apparent increase in virulence.
If West Nile virus were introduced into Australia, it would have to compete with Kunjin virus for vertebrate hosts and vectors. Because antibodies to Kunjin virus neutralise West Nile virus (and vice versa), it may prove more difficult for West Nile virus to become established or spread rapidly.
There is no treatment or vaccine available for West Nile infection, but people with prior exposure to Kunjin virus should be protected should there be an outbreak.
The experts believe it is important to maintain disinsection of aircraft and mosquito surveillance around major airports, as well as good internal surveillance for disease, to help protect against threats such as West Nile virus. However, they consider it would be difficult for West Nile virus to repeat in Australia the devastation it caused in North America.
The Medical Journal of Australia is a publication of the Australian Medical Association.
CONTACT: Professor John S Mackenzie, Telephone: 07 3365 4648 / 0439875 697,
Fax: 07 3365 6265, Email: micropara@biosci.uq.edu.au; John.Mackenzie@uq.edu.au
John Flannery (AMA) 0419 494 761 / 02 6270 5477