Introduction
Barmah Forest Virus causes infection in humans and other mammals. In humans, the infection results in polyarthritis, fever, tiredness, lethargy and rash. It has been identified only in Australia, and is named after the location in Victoria where it was first discovered in 1974.
It is clinically similar to Ross River Fever, but the symptoms tend to be less severe and of a shorter duration. Some patients, especially children, may be asymptomatic.
It is self-limiting, and treatment is usually supportive only. Most people recover within a few days, but in some cases, joint and muscle pain persists for up to 6 months.
It is most commonly seen in summer and autumn.
There are about 400 reported cases per year although the true prevalence is likely to be much greater. The short duration of illness, and asymptomatic nature means that many cases will go unreported. Over 50% of cases occur in Queensland.
Presentation
- Incubation period is about 3-11 days
- Polyarthritis – including joint pain and swelling
- Fevers
- Rash
- Headaches
- Tiredness
- Lethargy
Most cases last only a few days and patients are fit to return to work within a week.
Transmission
- Mosquito bites only
- Cannot spread directly from person to person
- Spread by multiple mosquito species
- Main reservoir of disease is in animals
- Mainly kangaroos and wallabies, but up to 30 species are implicated
- Be wary of mosquito breeding grounds in standing water – e.g. salt marshes, mangroves, and in standing water around the house – such as bird baths, plant pots and in buckets and containers around the house
- Mainly occurs in tropical areas in Queensland and the Northern Territory, but also frequently reports in NSW and Western Australia
- Much more common in rural areas
Diagnosis
- Confirmed with serological testing
Management
- No specific treatment
- Simple analgesia
- Gentle exercise may help to relieve joint pains
- Chronic fatigue occurs in a small minority of cases
Prevention
- Avoid getting bitten by mosquitos!
- Most bites occur in the early evening in warmer months
- Use insect repellents
- Wear light coloured clothing
- Use fly screens on windows and doors
- Check around the home for potential mosquito breeding areas
- Controlling mosquito breeding areas by local councils is effective at controlling outbreaks
References
- Barmah Forest Virus – Queensland Government
- Murtagh’s General Practice. 6th Ed. (2015) John Murtagh, Jill Rosenblatt