Murray Valley encephalitis

7-minute read

Key facts

Murray Valley encephalitis is a serious but rare illness spread via mosquitoes.
Most people who become infected have mild symptoms only or no symptoms at all.
Severe and potentially fatal symptoms include encephalitis (inflammation of the brain).
There is currently no vaccine or treatment available for Murray Valley encephalitis.
The best way to prevent infection is to avoid mosquito bites.

What is Murray Valley encephalitis?

Murray Valley encephalitis (MVE) is a serious but rare illness transmitted to humans via infected mosquitoes. Most reported cases of MVE have occurred in northern parts of Australia or Papua New Guinea.

What are the symptoms of Murray Valley encephalitis?

Many people with Murray Valley encephalitis have no symptoms.

Others have mild symptoms including:

fever
headache
muscle aches
nausea and vomiting

If you do have symptoms, they will usually start 7 to 12 days after infection.

Only about 1 in 1000 people bitten by infected mosquitos will develop a severe brain infection, known as called encephalitis (inflammation of the brain) or meningitis (inflammation of the brain lining and spinal cord).

Symptoms of encephalitis and meningitis include:

drowsiness
confusion
tremor
neck stiffness
seizures
coma

Babies who are infected may also become irritable or drowsy.

When should I call an ambulance or go to the emergency department?

If you have recently been in an area with reports of MVE, and you experience sudden symptoms, seek medical attention.

If you think you may have Murray Valley encephalitis, visit your nearest emergency department or call an ambulance on triple zero (000).

FIND A HEALTH SERVICE — The Service Finder can help you find doctors, pharmacies, hospitals and other health services.

What causes Murray Valley encephalitis?

MVE is a mosquito-borne virus. You can only catch it if you are bitten by an infected mosquito. You cannot catch it from other humans or animals, and you can only be infected once in your lifetime.

How is Murray Valley encephalitis diagnosed?

Your doctor can diagnose the infection with a blood test and a lumbar puncture (sample of fluid from around the spinal cord).

MVE is a notifiable disease. If you are infected, your doctor will notify the Department of Health, Disability and Ageing so they can try to control the virus’ spread and reduce its effect on the community.

How is Murray Valley encephalitis treated?

There is no vaccine or specific treatment for MVE.

Medicines are available to treat mild symptoms such as headache and fever. Some people may need treatment in hospital, if their symptoms are severe.

Your recovery time will depend on how severe your symptoms are. People with severe symptoms may take several months to fully recover.

What are the complications of Murray Valley encephalitis?

Severe illness can lead to death.

In people who recover, MVE can cause ongoing neurological (nerve) problems such as:

hearing loss
epilepsy
paralysis
brain damage

Can Murray Valley encephalitis be prevented?

There is no vaccine to prevent Murray Vally encephalitis. The best way to prevent MVE is to avoid being bitten by mosquitoes and midges.

Here are some ways to protect yourself:

Cover up as much skin as possible with loose, light-fitting clothes.
Stay inside in the early morning or at dusk, when mosquitos are most active.
Screen windows, doors and vents in living areas or tents, if camping.
Use insect repellent when you are outside and there are mosquitoes around.
Use other mosquito protective devices such as sprays or coils.

Mosquitos are common around swamps, marshes, rivers and other still water sources. If you are travelling in areas where mosquito-borne diseases are prevalent, speak to your doctor about how to best protect yourself.

You can also reduce your risk of being bitten by removing containers that hold water from your backyard and keeping any pools or ponds clean.

Biters infographic tile image — For more information on **insect bites**.

Resources and support

For information and any seasonal risk alerts, you can check the government pages of MVE relevant to your state and territory:

More information on staying safe around mosquitoes is provided by the Queensland Government, or the South Australian Government’s Fight the Bite.

The Victorian Government offers information on insect repellent, their use in young children and safety.

If you need advice on MVE, call healthdirect on 1800 022 222 to speak with a registered nurse, 24 hours, 7 days a week (known as NURSE-ON-CALL in Victoria).