Murray Valley encephalitis

Murray Valley encephalitis (MVE) is a serious but rare infection caused by the Murray Valley encephalitis virus. It is spread to humans by infected mosquitoes.

There is no vaccine and no specific treatment for MVE, so the best protection is to avoid mosquito bites.

Symptoms#

Most people infected with the virus have no symptoms, or only mild ones, and recover fully. Only a small number go on to develop serious illness.

When symptoms do appear, they usually start 7 to 12 days after an infected mosquito bite, though this can range from as little as 5 days to as long as 28 days. They may include:

• Fever
• Nausea and vomiting
• Headache, sometimes severe
• Neck stiffness
• Sensitivity to bright light (photophobia)
• Seizures or fits, especially in young children
• Drowsiness, confusion and muscle aches

A small number of people (about one in every 800) develop encephalitis, an inflammation or swelling of the brain. Severe infection can progress to loss of consciousness or coma, and may lead to brain damage or death.

Anyone with these symptoms should seek urgent medical attention.

How it spreads#

People become infected when bitten by a mosquito carrying the virus. Mosquitoes pick up the virus when feeding on water birds such as herons and egrets.

The virus is not spread directly from person to person, and you cannot catch it from contact with birds or other animals.

Where it occurs#

Murray Valley encephalitis virus is found in some regions, where human cases are reported from time to time. People who work, live or spend time outdoors in affected rural and riverine areas may be at increased risk.

Risk is highest during warmer, wetter periods, particularly after heavy rainfall or flooding, which increases the numbers of water birds and mosquitoes.

Diagnosis#

MVE can be diagnosed by testing the blood, by a lumbar puncture (also called a spinal tap), and/or by testing the urine. Testing can show recent or past infection, and repeat testing is usually needed to confirm the diagnosis.

Treatment#

There is no specific treatment for MVE. Care aims to support the person and ease symptoms, and some people may need treatment in hospital.

Preventing mosquito bites#

The best prevention is to protect yourself against mosquito bites:

• Cover up by wearing long, loose-fitting, light-coloured clothing.
• Use mosquito repellents containing picaridin or DEET on all exposed skin.
• Limit time outdoors when lots of mosquitoes are about.
• Remove stagnant water where mosquitoes can breed around your home or campsite.
• When travelling, make sure your accommodation has mosquito netting or screens.

Take extra care with children. Always check the repellent label. For babies, you may need to apply repellent to their clothes rather than their skin, and avoid putting it on the hands of babies or young children.

Key points#

• Murray Valley encephalitis (MVE) is a serious but rare infection caused by the Murray Valley encephalitis virus.
• There is no effective treatment or vaccine for MVE.
• The best prevention is to protect against mosquito bites.
• Symptoms can include fever, headache, neck stiffness and muscle aches.
• Anyone with symptoms should seek urgent medical attention.

Where to get help#