SWAT and scratch. The new sounds of summer are Sydneysiders trying to deal with the scourge of swarms of mosquitoes desperate for a taste of an exposed bit of skin.

Experts say prime breeding conditions developing after the warmest Spring on record, heavy rainfall in December and flooding of local wetlands by higher than expected tides has left the city in the grip of a mosquito frenzy.

And they warn more buzzing pests are on the way.

“This has been one of the worst starts to mosquito season in years,” Stephen Doggett, director of medical entomology at Westmead Hospital, said.

Scientists are also predicting an unusually high risk of an outbreak of dangerous mosquito-borne diseases such as the Ross River and Barmah Forest viruses along the NSW coast.

Dr Doggett said the mosquito season has started early this summer with prime breeding conditions developing after the warmest Spring on record, heavy rainfall in December and flooding of local wetlands by higher than expected tides.

media_camera Alivia sprays insect repellent on her daughter Demi, 5, to ward against swarms of mozzies which have descended on Sydney due to warm humid weather and recent rain.

The worst flying pest will be the saltmarsh mosquito, almost black in colour with striped legs, which is breeding in colossal numbers around Homebush Bay and in the mangroves and mudflats along the Georges River between Alfords Point and Bankstown.

They normally fly between 5km to 10km from breeding sites but have been recorded up to 50km from the mudflats.

Dr Doggett said above average numbers of mosquitoes are being recorded along the east coast. Each insect can lay more than 100 eggs.

“The mosquito-borne viruses won’t be a problem for Sydney because they need an animal host, usually a kangaroo or wallaby for Ross River virus,” he said.

“Normally the are about 300 to 400 cases along the coastal strip each year. But because we haven’t seen the viruses along the coast for several years, due to small numbers of saltmarsh mosquitoes, I think the risk is up there as one of the highest for some years.

“This will be a risk year for the viruses.”

Even Sydney hospitals are not immune from the flying scourge.

A visitor to Liverpool Hospital said they had seen mozzies in the Emergency Department waiting area and in a treatment room on Christmas Day.

The same person said they also saw the insects a day later in a surgical ward and last week spoke to a new mother in the maternity ward who asked her husband to bring in a mosquito net to protect their newborn baby from mosquitoes.

A South Western Sydney Local Health District spokeswoman confirmed that an area near one of the exits to the Emergency Department at Liverpool was sprayed with insect repellent after staff noticed mosquitoes.