Health Hazard Warnings Issued in NSW and South Australia as Mosquito Population Skyrockets

This close-up photograph shows a mosquito in Montlouis-sur-Loire, central France, on October 21, 2022. Guillaume Souvant/AFP via Getty Images

Health authorities in New South Wales (NSW) and South Australia have warned their residents to avoid getting bitten by mosquitoes as flooding and summer weather conditions have caused dangerous mosquito-borne viruses to emerge in the two states.

On Jan. 11, NSW Health announced that the potentially fatal Murray Valley encephalitis (MVE) virus was detected in a mosquito in Menindee, a small town in the far west of the state.

The agency said the recent floods and rain in the area were most likely behind the emergence of the virus.

While the primary hosts of the MVE virus are waterbirds such as herons and egrets, it is not transmitted via touching an infected animal or eating animal products.

In addition, people cannot catch the virus from another person.

Health Protection NSW executive director Richard Broome said while many people do not display any symptoms after getting infected with the virus, some will develop a severe infection and even neurological problems in some rare cases.

“Only a small proportion of people infected with the virus will experience symptoms, which include fever, headache, nausea, vomiting, loss of appetite, diarrhoea, and muscle aches,” Broome said.

“Among those who get a severe infection, some may die or have lifelong neurological complications.”

Currently, there are no vaccines or effective treatments for MEV. Therefore, the best way to prevent infection is to avoid mosquito bites.

“Avoiding mosquito bites will also protect against other mosquito-borne infections, including Japanese encephalitis, Ross River Fever and Barmah Forest virus,” Broome said.

The last time that infected cases in humans were identified in NSW was in 2011.

Mosquito Boom in South Australia

Meanwhile, South Australia Health has issued a warning for the state residents after finding the number of mosquitoes carrying the Ross River virus and Barmah Forest virus in the state surging by five times.

Both viruses can cause a similar range of symptoms in humans, including fever, chills, headache, muscle and joint pains, stiffness or swelling, and rashes.

These symptoms appear seven to ten days after the infected get bitten by mosquitoes and will normally fade off after a few weeks. However, some people may suffer joint pain and severe tiredness for many months.

At the same time, the health authority discovered high to extreme numbers of a mosquito species carrying several dangerous viruses, such as Japanese encephalitis, Murray Valley encephalitis and West Nile Virus, in the Mallee region, west of Adelaide.

The Japanese encephalitis virus cannot be transmitted from infected animals to humans, between humans and humans, or via eating meat from infected animals.

While the virus normally does not cause any symptoms after infection, some people may develop brain inflammation, which can cause permanent damage to the nervous system or even death in some rare cases.

At present, there are vaccines for Japanese encephalitis. However, no vaccinations nor cures are available for the Ross River and Barmah Forest viruses.

Flooding at Scott’s Creek, in South Australia, on Dec. 30, 2022. AAP Image/Matt Turner

South Australian Chief Health Officer Nicola Spurrier said this summer was potentially the worst season in the state with all the mosquito-borne viruses detected.

“We’ve got all the elements combining … with the water, the flooding, cold spring, wet spring and now a hot summer. We are seeing the mosquito population really booming,” she said.

In the face of the mosquito boom, the chief health officer called on people to take measures to avoid getting bitten.

How to Protect Yourself from Mosquitoes

According to NSW Health, people can avoid mosquito bites by doing the following things:

• Covering windows and doors with insect screens and making sure there are no gaps in them
• Getting rid of items that might be the breeding ground for mosquitoes outside your house, such as old tyres and empty pots
• Improving drainage to remove stagnant water on your property
• Wearing light, loose-fitting, and long-sleeved clothing, including footwear and socks, especially around dusk and dawn
• Applying repellent to all areas of exposed skin regularly
• Using insecticide sprays, vapour dispensing units and mosquito coils to repel mosquitos