Health authorities in the Northern Territory have issued warnings for residents and visitors to avoid mosquito bites after two people from Alice Springs died from Murray Valley encephalitis.

It’s a reminder that mosquitoes in many parts of Australia can be more than just a nuisance.

Without a vaccine for Murray Valley encephalitis, preventing disease relies on preventing mosquito bites.

What is Murray Valley encephalitis virus?

The virus takes its name from the Murray Valley in southeastern Australia where it was first identified in patients who died during an outbreak in 1951.

Infections are rare, but can be deadly. Most people infected don’t develop symptoms. For those that do, symptoms can range from fever and headache to encephalitis (inflammation of the brain), with coma and paralysis. Around 40% of people who develop symptoms won’t fully recover and about 25% die.

The virus circulates between water birds and mosquitoes, most commonly Culex annulirostris, but a small number of other species may be involved too.

The virus is detected most years in northern Australia, most notably the Kimberley in Western Australia and the Top End of the Northern Territory.

But when environmental conditions are favourable, the virus can emerge in southern regions of Australia. These conditions are generally associated with increased rainfall and flooding generally brought on by La Niña influenced weather patterns.

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