Murray Valley encephalitis

Murray Valley encephalitis (MVE) is an uncommon but potentially fatal disease that occurs after being bitten by a mosquito carrying the MVE virus. It is the most serious mosquito-borne disease that occurs in the Northern Territory (NT). 

How MVE is spread

The MVE virus is spread by the bite of an infected mosquito (usually Culex annulirostris, also known as the common-banded mosquito). Only about 1 person in 1000 who is bitten by an infected mosquito will become unwell with MVE.

Where MVE usually occurs

Although MVE can occur throughout Australia, it is most common in northern Australia. The MVE virus is present from February to July in the Top End of the NT, north-west of Western Australia and inland North Queensland during most years, and can extend into the Barkly and Central Australia in wet years. 

Most cases are detected between March and May.

Symptoms

Symptoms of MVE usually appear 5 to 28 days after being bitten by an infected mosquito. The early symptoms include headache, fever, nausea and vomiting, and muscle aches, which can progress to drowsiness, confusion, seizures or fits (especially in young children) and in severe cases delirium and coma.  

Who is at risk

People most at risk are babies, young children and newcomers to a region where MVE occurs.

Diagnosis

A blood test is available to test for recent or past MVE infection.

Treatment

There is no specific treatment or vaccine available for MVE. The treatment of severe MVE is supportive and often requires admission to an intensive care unit. 

Prevention

The only protection from MVE is to avoid being bitten by mosquitoes. Everyone should take measures to avoid being bitten by mosquitoes, particularly those visiting and camping in or near swamp or river systems during the evening and night, and in rural areas near sites of relatively high mosquito activity.

Mosquito protection for young children and babies is absolutely essential.

Personal protective measures

For self protection from mosquitoes in areas and times of actual or potential mosquito activity:

  • 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 protective clothing in outdoor situations including covering feet, legs and arms. Loose, light coloured clothing is best
  • use personal repellents containing DEET or picaridin 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.

Contact

For more information contact your nearest Centre for Disease Control.

Last updated: 27 June 2017