Barmah Forest virus
Barmah Forest virus (BFV) is a disease spread by infected mosquitoes.
Mosquitoes live longer in humid conditions so it allows them to live long enough to pass it on to humans.
In the Northern Territory (NT), it is the second most common arbovirus after Ross River virus (RRV).
It is characterised by painful or swollen joints lasting from days to months.
Where it's found
BFV was first isolated in northern Victoria and has been detected in most parts of mainland Australia.
In the NT, BFV has a high risk from December to May.
The highest risk is usually in February when there is large numbers of mosquitoes from high tides or increased rainfall.
Since 1992, there have been between 11 to 130 cases reported annually in the NT.
How it spreads
BFV infection cannot be spread from person to person.
The virus is transmitted to humans by the bite of an infected mosquito.
The mosquitoes in the NT that can spread the virus are:
- Aedes vigilax (salt marsh mosquito)
- Culex annulirostris (common banded mosquito)
- Aedes normanensis (flood water mosquito)
- Aedes notoscriptus (backyard mosquito).
Symptoms
Symptoms vary from person to person and most commonly appear within 3 to 11 days after being bitten.
Although the symptoms of BFV are similar to those of RRV disease, the disease is generally milder.
Many people, particularly children, even if bitten by an infected mosquito, do not develop any symptoms of the disease.
Symptoms include:
- painful (sometimes swollen) joints - most commonly the ankles, fingers, knees and wrists
- muscle and tendon pain
- raised red rash affecting mostly limbs and trunk (this may be more florid than the rash of RRV)
- fever
- fatigue
- headache.
Fever, nausea and skin rash usually disappear within the first 1 or 2 weeks of illness. In a minority of cases lethargy, joint, muscle and tendon pain may last for over 6 months.
Symptoms subside eventually and leave few or no after-effects. It is not possible at present to say how long an individual person will take to get better.
As a rule, once you have had BFV once, you will not get it again.
Diagnosis
BFV infection is diagnosed by a blood test.
Treatment
There is no medical cure for the disease.
Medical treatment is aimed at:
- easing joint pains and swelling,
- minimising fatigue and lethargy.
For some people, simple painkillers like aspirin or paracetamol are sufficient. Others will require stronger medications to ease the inflammation.
Emotional stress, physical fatigue and alcohol may cause symptoms to worsen or to last longer.
Prevention
Try to reduce the number of places on your property where mosquitoes can breed.
Any pools of water, even if tiny, can provide breeding sites for mosquitoes.
The only protection from BFV is to avoid being bitten by mosquitoes. There is no vaccine.
Personal protective measures
- stay indoors when mosquitoes are most active, from just before, until 2 hours after sunset
- ensure flyscreens in houses or caravans are in good condition
- if camping out sleep in a mosquito-proof tent or under a mosquito net. Repellents only protect against mosquito bites for up to four hours, not all night
- avoid scents on the body, e.g. perfume, deodorants, and sweat, since these can attract mosquitoes
- use personal repellents containing DEET, picaridin or PMD (extract of lemon eucalypt) on areas of exposed skin in combination with protective clothing
- use electric insecticide devices using repellent treated pads in indoor or enclosed areas
- use mosquito coils, or candle heated or gas operated devices using insecticide treated pads for patio and veranda or relatively sheltered or low wind outdoor situations.
Read more about protecting yourself against mosquitoes.
Information for health professionals
To find out more, go to the NT Health website.
Contact
Contact your nearest Centre for Disease Control on the NT Health website.