HNEH Public Health Physician Dr David Durrheim said recent warm weather together with good rainfall had resulted in excellent breeding conditions for mosquitoes responsible for spreading Ross River virus and Barmah Forest virus.

"Good rainfall during the past few weeks has provided ample breeding sites and contributed to a rise in mosquito numbers, while the warm weather allows mosquitoes to survive longer and transmit the viruses to people," Dr Durrheim said.

The only way to prevent infection is to avoid being bitten by mosquitoes. "These viruses are spread by mosquitoes that feed on animals that have the infection, so prevention depends on avoiding mosquito bites, especially in summer and autumn months when infections peak," Dr Durrheim said.

"The symptoms of Ross River virus and Barmah Forest virus infection include fever, skin rash, painful joints and tiredness," he said.

"Most people affected will have a mild illness that lasts for a few days. However, in some people, joint aches and lethargy can last for months." Methods for avoiding mosquito bites include:

. Avoid being outside unprotected before dawn and after dusk.

. Avoid known high risk breeding sites, including marsh areas.

. When outside wear loose fitting, light coloured clothing that cover your arms and legs.

. Use an insect repellent that contains the chemical DEET or picaridin on exposed skin.

. Fit and maintain fly screens to all windows and doors.

. If mosquitoes are inside use a knockdown insecticide in bedrooms half an hour before going to bed according to instructions.

For more information, visit https://www.health.nsw.gov.au/Infectious/factsheets/Pages/mosquito.aspx