Rise in Ross River virus

Safeguard yourself against mosquitoes this summer. (iStock)

Queenslanders are being urged to be extra vigilant against mosquitos after a significant rise in Ross River virus cases has been observed.

Queensland Health has issued a warning of a heightened risk of Ross River virus infections across the state after surveillance activities revealed a sharp rise in detections of mosquitoes carrying the virus.

Queensland Chief Health Officer Dr John Gerrard said there had been a very high number of Ross River virus detections in mosquitoes across nine different local government areas stretching from Mackay down to south-east Queensland in recent weeks.

Ross River Virus is a reportable virus and in the Darling Downs Hospital and Health Service region, which includes the South Burnett, there have been two cases of Ross River virus reported between 1 January and 4 February 2024.

In the Wide Bay Hospital and Health Service region, which incorporates the North Burnett, there have been five cases of Ross River virus for the same time period.

Across Queensland there has been 64 cases of Ross River virus this year.

“Queensland Health, together with local government partners, routinely collects mosquito samples and tests them for Ross River virus infection. This season, more than 700 mosquito trap collections have been tested for Ross River virus,” Dr Gerrard said.

“We have been notified of 31 positive mosquito traps across the state so far, which is more than the total we saw over the 2019-20 summer months when there was a significant Ross River virus outbreak. In 2020, 3381 cases of Ross River virus were recorded.

Dr Gerrard said it was concerning to see such a high number of Ross River virus detections in mosquito populations this early in a typical season.

“This is an indicator of elevated virus activity,” he said.

“Typically, Ross River virus infection begins to rise with the onset of rain and warm temperatures in December before peaking in February and March. It is also typical to see a significant number of Ross River virus cases every three to four years, so we are on track for a spike in cases,” he said.

“Given high mosquito numbers combined with these latest surveillance results, we know there is a heightened risk of human exposure to mosquitoes carrying this virus right across Queensland.”

The state’s Chief Health Officer shared that it was critical for people to take measures to protect themselves from mosquito bites and mosquito-borne diseases.

“There’s no vaccine or specific antiviral treatment available for Ross River virus, so prevention is key. The most important measure you can do against mosquito-borne disease is to take steps to avoid getting bitten,” Dr Gerrard said.

“We know there’s a lot of mosquitoes around at the moment due to the hot and wet conditions. Remember that any mosquito could be carrying Ross River virus – the more you get bitten, the more likely you will be infected.”

The Ross River virus can be found in more than 40 different species of mosquitoes across Australia.

“If you’re enjoying the great outdoors this summer to play sport, go for bushwalks, catch up on gardening or even hosting a backyard barbecue, you need to be vigilant of mosquitoes,” Dr Gerrard said.

“Biting can be experienced at any time of day, but some species are most active at dusk and dawn. It’s best to avoid outdoor activities when mosquitoes are most active.”

Queenslanders can prevent mosquito bites by regularly applying insect repellent containing DEET, picardin or oil of lemon eucalyptus and wearing loose, light-coloured clothing to cover up arms, legs and feet.

“Around your home, you should empty containers holding water or remove standing water, wherever possible, at least weekly and ensure flyscreens are in good order so mosquitoes can’t enter your home easily,” he said.

Symptoms of Ross River virus may include fever, swollen and painful joints and rash. Treatment is supportive and involves managing the symptoms that develop.

While most people recover in a few weeks, some people experience joint pain and fatigue for months after infection.

The virus is spread when a mosquito bites an infected animal. Humans are infected when they are bitten by infected mosquitoes, not from person to person.

Ross River virus infections account for the largest number of human mosquito-borne disease notifications in Queensland.

In 2023, there were 699 cases of Ross River virus infection recorded across the state. Statewide, there has been 64 cases notified in January.