Most people infected with the viral infection do not have symptoms or have only mild symptoms.

However, a small number may experience fever, drowsiness, headache, stiff neck, nausea and dizziness, though a fever may be the only sign of early infection in children. Anyone experiencing symptoms should seek urgent medical advice.

Managing scientist Andrew Jardine said many people were being bitten while fishing and camping.

He encouraged people to pack an effective repellent.

“Ross River and Murray Valley encephalitis viruses are only spread by mosquitoes – so the message is simple: protect yourself from being bitten,” Doctor Jardine said.

“While the risk of getting infected and becoming sick is low, the illness caused by the virus can be severe in some cases.”

Mosquitos are most active at dawn and early evenings, so people are encouraged to stay indoors at those times.

Long, loose fitting and light-coloured clothing is also recommended, while babies and children should also be dressed in suitable clothing, including socks and shoes.

Bed and pram netting is also encouraged, as well as insect screens on houses and caravans and the use of effective mosquito repellents containing diethyloluamide, picaridin or Oil of Lemon Eucalyptus (also known as PMD).

Keeping grass and other vegetation short is another way to help keep mosquitoes away from homes.

Japanese encephalitis was also detected in WA last year and remains a potential risk in northern WA.

JE is vaccine preventable, unlike MVE and RRV.