Australians are being urged to prevent mosquito bites this summer, with warmer temperatures increasing the risk of Ross River Virus outbreaks.
The risk of outbreaks with warmer temperatures is especially heightened in river land and coastal regions, research mapping studies from across the country has found.
“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. While not all mosquitos carry Ross River Fever, it’s wise to be careful,” said University of Adelaide Public health researcher Christina Mary Varghese.
Precautions may include wearing light coloured clothing, using mosquito nets and mosquito repellent creams on unexposed skin, particularly while travelling and camping outdoors in summer.
A common mosquito-borne disease in Australia, around 3,000 cases of Ross River Virus are reported annually. It can be spread by more than 40 different species of mosquitos, and hosts can include kangaroos, wallabies, bats, horses, and dogs.
While most people recover within weeks from symptoms which include rash, fever and joint pain (arthralgia), in some cases symptoms, specifically joint pain, can persist hindering quality of life.
Geographic distribution variations
Ross River Virus risk increases when temperatures rise, but there are differences across geographic regions according to the scoping review led by the University of Adelaide. The review published in the Australian and New Zealand Journal of Public Health analysed 30 studies related to the virus and temperature in Australia.
Maximum temperatures were linked to higher Ross River Virus cases in coastal Australia, particularly in Queensland, New South Wales, Tasmania and WA.
However, some studies also found that minimum temperatures appeared to increase the risk of the Ross River Virus infections in Darwin and in some inland regions of SA, Victoria and Queensland.
“It is very hard to predict Ross River Virus outbreaks, with a complex range of factors contributing to increased risk, including rainfall, humidity, and stagnant water conditions,” said lead author Christina Mary Varghese.
“But we know that cases are more likely when temperatures are between 17 and 31 degrees, with infections spiking when temperatures are around 26 degrees.
“That’s why it’s important for Australians to protect themselves from mozzie bites over the Christmas and New Year period.”
Mosquitos can also cause illnesses such Barmah Forest Virus and Japanese Encephalitis, she said.
The study also looked at the evidence on Barmah Forest Virus, another common mosquito-spread virus, finding that the risk was linked to minimum temperatures in both coastal and inland areas.
“One of our biggest findings was that studies of Ross River Virus and Barmah Forest Virus have mostly centred on the coast. There is very little data on smaller towns and few related to Ross River Virus in Queensland,” said Ms Varghese.
The study also exposed a knowledge gap about how the number of cases in different regions might be influenced by climate change scenarios.
“There has been no Australian based study assessing associated healthcare costs, nor projecting future disease burden under different climate change scenarios – this is a key knowledge gap that needs to be addressed,” said University of Adelaide Professor Peng Bi.
“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.”
Australia’s new Centre for Disease Control, due to launch officially in January, will watch these issues closely said Public Health Association of Australia CEO Terry Slevin.
“As the Australian weather warms due to climate change, we are likely to see different parts of Australia exposed to mosquito carried diseases like Ross River Fever and Barmah River Virus. Australia’s Centre for Disease Control will be monitoring these issues and is already providing advice on mosquito bite prevention.”
The Australian Centre for Disease Control offers tips for prevention mosquito bites here.
The impact of temperature on Ross River virus and Barmah Forest virus infection in Australia: A scoping review” has been published in the Australian and New Zealand Journal of Public Health here.
