WA is being warned to brace for an invasion of march flies and mosquitoes, with warm, wet weather combining for perfect breeding conditions.
The Department of Health has issued the warning for visitors and residents in regional WA, saying bites could cause serious allergic reactions, and the mosquito-borne Ross River virus and Barmah Forest virus.
A growing number of march flies has been reported from various regions of WA, including the northern Goldfields and Pilbara regions.
The bite of at least one march fly species - Mesomyia tryphera - can cause serious allergic reactions in some people.
"In rare cases, people may experience serious symptoms including hives, fever, wheezing and even anaphylaxis," said entomologist Dr Peter Neville today.
The recent rain and flooding in the Kimberley and Pilbara regions is also set to increase mosquito breeding.
"It is not possible to keep mosquitoes and other biting insects below nuisance levels across extensive rural areas of WA," Dr Neville said.
Symptoms of mosquito-borne infection include painful or swollen joints, sore muscles, skin rashes, fever, fatigue and headaches.
There is no cure for the viruses and symptoms can last for weeks or months.
People are warned to avoid outdoor exposure if large numbers of biting insects are around, to wear protective clothing when outdoors and apply repellent.