Murray Valley encephalitis

Murray Valley encephalitis (sometimes known as MVE) is a serious but rare disease caused by the mosquito-borne Murray Valley encephalitis virus. This virus is most often found in Australia and Papua New Guinea.

Sometimes, the virus can affect the central nervous system. This can lead to serious conditions such as:

• encephalitis — inflammation of the brain
• meningitis — inflammation of the lining around the brain and spinal cord
• myelitis — inflammation of the spinal cord

Many people with Murray Valley encephalitis have no symptoms. Some have mild or severe symptoms. Symptoms usually appear 5 to 28 days after infection.

Mild symptoms

Mild symptoms include:

• fever
• headache
• stiff neck
• sensitivity to light
• nausea

Severe symptoms

Sometimes, the virus can affect the brain, spinal cord or the tissues around them. This can lead to serious illness. Symptoms of encephalitis, meningitis or myelitis may include:

• drowsiness (feeling unusually sleepy)
• confusion
• tremor (shaking you cannot control)
• neck stiffness
• weakness
• seizures
• paralysis (being unable to move part of your body)

Babies who are infected may also become irritable or floppy.

Murray Valley encephalitis is a mosquito-borne virus. This means that 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.

Sometimes, the virus may spread from mother to baby during pregnancy. It may also spread through blood transfusions or needle-stick injuries.

See your doctor promptly if you have recently been in an area where Murray Valley encephalitis has been reported and you develop any mild symptoms such as:

• fever
• headache
• nausea

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

Murray Valley encephalitis is a notifiable disease. If you are infected, your doctor will notify the Australian Centre for Disease Control (CDC). This helps them track the virus and prevent further spread.

There is no vaccine or treatment for Murray Valley encephalitis.

Medicines may help relieve mild symptoms such as headache and fever. If you develop severe symptoms, you may need treatment in hospital.

Severe Murray Valley encephalitis can be life-threatening and lead to death if it causes inflammation of the brain, spinal cord or the tissues around them.

People who get better from severe Murray Valley encephalitis may have long-term neurological (brain or nerve) problems, such as:

• hearing loss
• epilepsy
• problems with movement, memory or learning

There is no vaccine to prevent Murray Valley encephalitis. The best way to prevent Murray Valley encephalitis is to avoid being bitten by mosquitoes.

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

• Australian Capital Territory (Opens in new tab)
• New South Wales (Opens in new tab)
• Northern Territory (Opens in new tab)
• Queensland (Opens in new tab)
• South Australia (Opens in new tab)
• Tasmania (Opens in new tab)
• Victoria (Opens in new tab)
• Western Australia (Opens in new tab)

Queensland Government and the South Australian Government's Mozzies Suck (Opens in new tab) campaign have more information on staying safe around mosquitoes (Opens in new tab).

The Victorian Government offers information on insect repellent (Opens in new tab) and its safe use in young children.

Languages other than English

NSW Health has a guide to Murray Valley encephalitis (Opens in new tab) in community languages.

Information for Aboriginal and/or Torres Strait Islander peoples

NSW Health has mosquito information resources (Opens in new tab) for Aboriginal and/or Torres Strait Islander peoples.