Ross River outbreak risk rises summer temperatures

Ross River Virus outbreaks are going up with the temperature this summer, especially in riverland and coastal regions, a new scientific review says.

The risk was identified in a scoping review of 30 studies into the mosquito-borne virus and temperature by the University of Adelaide.

It also uncovered a lack of understanding on the link between warmer temperatures and virus cases within inland areas of the country.

The review was published in the Australian and New Zealand Journal of Public Health, the official publication of the Public Health Association of Australia.

Researchers conducting the scoping review found that the virus risk increases when temperatures rise but with differences across different regions, lead author Christina Mary Varghese, of the University of Adelaide, says.

“Studies found that maximum temperatures are linked to higher virus cases in coastal Australia particularly in Queensland (Brisbane, Cairns, Townsville, Mackay, Gladstone, Bundaberg, Redland and Darling Downs), New South Wales (North-East NSW), Tasmania (Sorell region), and WA (Mandurah),” she says.

“Some studies found that minimum temperature appeared to increase the risk of the infections in Darwin and in some inland regions of SA, Victoria and Queensland.”

She says it remains “very hard” to predict outbreaks given the different factors that increase the risk like rainfall, humidity and stagnant water.

“We know that cases are more likely when temperatures are between 17 and 31 degrees with infections spiking when temperatures are around 26 degrees,” she says.

“That’s why it’s important for Australians to protect themselves from mozzie bites over the Christmas and New Year period.”

The study also looked at the common mosquito-spread Barmah Forest Virus and found that the risk was linked to minimum temperatures in coastal and inland areas.

“One of our biggest findings was that studies of (both) viruses mostly centred on the coast. There is very little data on smaller towns and few related to Ross River Virus in Queensland,” Varghese says.

“We need to better understand how our changing climate is going to
influence risk in different regions.” Professor Peng Bi, University of Adelaide

PRECAUTIONS YOU CAN TAKE

During summer, travel and camping, researchers say light-coloured clothing should be worn and mosquito nets and repellent creams used.

“When it’s summer holidays more of us are likely to be out and about, swimming, camping, and fishing, increasing the risk of mosquito bites,” she says.

“While not all mosquitos carry Ross River Fever, it’s wise to be careful. Mosquitos can also cause illnesses such Barmah Forest Virus and Japanese Encephalitis.”

Senior author Professor Peng Bi, School of Public Health, University of Adelaide, says that the study also exposed a knowledge gap about how case numbers in different regions might be influenced by climate change.

“There has been no Australian study assessing associated health care costs, nor projecting future disease burden under different climate change scenarios – this is a key knowledge gap that needs to be addressed,” he says.

“We need to better understand how our changing climate is going to influence risk in different regions.”

“We also need to fill the big gaps in research across inland Australia – so we can track how things change over time.”

Terry Slevin, CEO of the Public Health Association of Australia, says a new Centre for Disease Control, due to launch in January, will need to keep a close watch.

“As the weather warms, we are likely to see different parts of Australia exposed to mosquito carried diseases like Ross River Fever and Barnah River Virus.”