Mosquito warning as Ross River cases rise

Victorians are being warned to protect themselves from mosquito bites with increased numbers of cases of Ross River virus notified to the Department of Health this summer.

Victoria’s Executive Director for Communicable Disease, Dr Bruce Bolam, said there have been 448 cases of Ross River virus across the State to February 25. In a typical year, about 200 cases are notified to the department. In contrast, almost 2000 cases were notified in 2017 after widespread springtime flooding in late-2016 created massive mosquito breeding sites. This summer, the majority of the cases have been in residents of the Surf Coast, Bellarine and East Gippsland areas.

A viral infection transmitted through mosquito bites, Ross River virus disease occurs throughout most regions of Australia, particularly around inland waterways and coastal regions. Heavy rainfall, floods, high tides and warm weather increase mosquito numbers, resulting in higher numbers of cases.


Dr Bolam said the early summer conditions, particularly in coastal areas, were conducive to mosquito breeding. The virus is passed between mosquitoes and certain animals, such as wallabies and kangaroos. Infected mosquitoes can then bite people, making them unwell.

Symptoms of Ross River virus can include fever, rash, headache, aching muscles and/or joints and fatigue. People experiencing symptoms should seek medical attention from their GP.

Onset of symptoms may be from 2 to 14 days following a bite from an infected mosquito. There is no evidence that Ross River virus can be spread directly from one person to another.

Many local councils work routinely with the department to monitor and limit mosquito numbers. Around 12 councils currently participate in the state mosquito-borne disease program and receive funding for mosquito surveillance and vector control.

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Mosquito traps are set up in the field, and the mosquitoes that are caught are sent to Melbourne for testing. “When mosquito numbers are high, and the lab detects virus in these mosquitoes, there might be an increased risk of acquiring Ross River virus in the coming days if the weather conditions are favourable,” Dr Bolam said.

“Mosquitoes need stagnant water to breed, but they also prefer mild, calm, and more humid air to fly and bite.” Dr Bolam said people can take simple steps to avoid bites and protect themselves and their family against mosquito-borne diseases. “Victorian mosquitoes can be active throughout the day, but the peak period is often around the late afternoon and into the evening as well as around dawn and dusk,” he said.

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“Everyone is encouraged to wear long, loose fitting clothes and use repellents containing picaridin or DEET on exposed skin.” “People should ensure that insect screens fitted to doors and windows around the home are in good condition.

“Mosquito numbers can be reduced by getting rid of stagnant water around the home or campsites. Mosquitoes will breed in any receptacle that can hold water, including old tyres, fish ponds, unmaintained swimming pools, unsealed water tanks and pot plant holders.”