What is Barmah Forest virus?
Barmah Forest infection is caused by a virus that is spread by mosquitoes.
What are the symptoms?
- Fever, chills, headache and muscle pain.
- Joint swelling, stiffness and pain, especially in the mornings.
- A rash, usually on the trunk or limbs. The rash usually lasts for 7 - 10 days.
- A feeling of tiredness or weakness.
Symptoms usually develop about 7-10 days after being bitten by an infected mosquito. Many people with the infection do not develop any symptoms of the disease.
The majority of people with Barmah Forest virus infection recover completely in a few weeks. Others may experience symptoms such as joint pain and tiredness for many months.
How is it spread?
People develop Barmah Forest virus infection after being bitten by a mosquito that is infected with the virus. The virus is not spread directly from person to person.
Who is at risk?
As mosquitoes spread the infection to people, anyone bitten is at risk of infection if they are not immune. The virus is found in mosquitoes at different times of the year and the level of virus in mosquitoes varies from year to year. Warm, wet weather encourages mosquito breeding and increases the risk of infection. Most human cases occur during March and April when a higher proportion of mosquitoes carry the virus. Although coastal areas of northern NSW have the highest rates of infection, cases can also occur inland.
How is it prevented?
Avoid being bitten by mosquitoes. Mosquitoes that carry the virus are usually most active in the hours after sunset and again around dawn.
- When outside cover up as much as possible with light-coloured, loose-fitting clothing and covered footwear.
- Use an effective repellent on all exposed skin. Re-apply repellent within a few hours, according to instructions, as protection wears off from perspiration, particularly on hot nights or during exercise. The best mosquito repellents contain Diethyl Toluamide (DEET) or picaridin. Botanical based products (e.g. Eucalyptus, Citronella) provide only limited periods of protection.
- The stronger the concentration of an insect repellent, the less frequently it will need to be applied to stop mosquito bites. Repellents containing low concentrations of DEET or picaridin provide shorter periods of protection and need to be reapplied more frequently so it's important to read the product information.
- Cover your clothes with repellent as mosquitoes can bite through material, but be careful, some repellents stain clothes.
- Topical repellents are not recommended for use on children under 3 months. Use of physical barriers such as netting of prams, cots and play areas is preferred. Repellents containing less than 10% DEET or picaridin are safe for older children if applied according instructions. Parents or carers should apply repellent.
- Note that prolonged or excessive use of repellents can be dangerous, particularly on babies and young children. Avoid putting repellent near eyes and mouth, spread sparingly over the skin.
- Use mosquito coils outdoors and use vaporising mats indoors. Note, however, that devices that use light to attract and electrocute insects have not been proved to be effective in reducing mosquito numbers.
- Cover all windows, doors, chimneys, vents and other entrances with insect screens.
- Sleep under mosquito bed nets at night.
- When camping, use flyscreens on caravans and tents or sleep under mosquito nets.
How is it diagnosed?
Your doctor can take a blood sample and have it tested for antibodies against Barmah Forest virus. While a single test that measures IgM antibody can give some indication of a recent infection, this test is often falsely positive and does not necessarily indicate Barmah Forest virus infection. A second specimen taken 14 days later is recommended to confirm a recent infection.
How is it treated?
There is no specific treatment for Barmah Forest virus infection.
Your doctor will be able to advise you on treating the symptoms with anti-inflammatory medications.
What is the public health response?
Laboratories are required to notify cases of Barmah Forest virus on diagnosis. Where cases occur in unexpected locations, the public health unit may investigate further.
For further information please call your local Public Health Unit on 1300 066 055