What is Epidemic Polyarthritis (Ross River virus)

Ross River virus, or as it is traditionally called Epidemic Polyarthritis, is caused by a virus which is transmitted to humans through the bite of mosquitoes. A wide variety of symptoms may occur from rashes with fevers, to arthritis that can last from months to years. There are no specific treatments and actions which reduce mosquito bites are the best form of prevention against these debilitating diseases. The disease affects the joints and the skin.

Statistics on Epidemic Polyarthritis (Ross River virus)

RR disease is the most commonly transmitted mosquito-borne viral disease to humans in Australia. The number of cases has averaged >5,000 per annum during 1991-1997. The virus appears to be endemic in most rural areas, and there has been an increasing incidence near major cities. For most of Australia, peak incidence of the diseases is through the summer and autumn months, particularly from January through to March, when the mosquito vectors are most abundant. However, in southwestern Australia and eastern Victoria, RR activity often begins in the spring months and peaks in early summer. Areas under intensive irrigation and localities close to saltmarshes, are most productive for mosquito populations and hence tend to result in the highest number of human cases of disease. Outbreaks occur when local conditions of rainfall, tides and temperature promote vector abundance.

Risk Factors for Epidemic Polyarthritis (Ross River virus)

Serological studies and laboratory investigations have indicated that native mammals, most likely kangaroos and wallabies, are natural hosts for RR virus.
RR virus transmission from human to mosquito to human (thus occurring without the involvement of an animal) has been proposed, and there is now little doubt that such a cycle involving only humans and mosquitoes occurs during periods of intense virus activity.
Predisposing factors are related to being in contact with known mosquito habitats. In warm, humid climates near bodies of water people will be most at risk of a mosquito bite and as a consequence the Ross River virus.
Individuals not using protective mosquito nets or insect repellants are at higher risk of being bitten by a mosquito carrying the virus.

Progression of Epidemic Polyarthritis (Ross River virus)

The disease usually begins as a viral illness with fever and malaise, but can then lead to symptoms of joint pains (arthritis) usually involving many joints. The symptoms can last for months, or even years.

Prognosis of Epidemic Polyarthritis (Ross River virus)

There is no known cure for this viral infection. Despite the fact that it can cause an arthritis which is long-standing the disease is, however, not fatal and arthritic symptoms can resolve themseleves in a number of months/years.

How is Epidemic Polyarthritis (Ross River virus) Treated?

1. Treatment:
Specific therapies do not exist to treat the disease, rather it is the symptoms that are alleviated. This includes various analgesics to reduce the pain and fevers, and anti-inflammatory agents for the arthritic symptoms.
2. Prevention:
Prevention of mosquito borne viral diseases is mainly accomplished through reducing the threat of bites from mosquitoes. This can be achieved either through undertaking active mosquito control or by the use of personal protective measures. There are large scale control measures which can only be undertaken by government bodies, generally local councils. On a small scale, householders can ensure that their own backyard does not contain water holding containers which can provide suitable mosquito larval habitats (e.g. undrained pot plants, blocked gutters, disused bottles, old tyres, etc). Personal protective measures include: avoiding known mosquito infested areas, especially at dawn and dusk when mosquitoes are most active; ensuring that houses are adequately screened; using insect repellents that contain the chemical DEET, and reapplying it regularly; and wearing long sleeved shirts and pants.

Epidemic Polyarthritis (Ross River virus) References

[1] Department of Medical Entomology University of NSW.
[2] Kay, B.H. and Aaskov, J.G. (1988). Ross River Virus Disease (Epidemic Polyarthritis). in Monath, T. (ed). The Arboviruses: Epidemiology and Ecology, Volume IV. CRC Press, Florida, pg: 93-112.

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