HNELHD is concerned the animals could carry serious diseases and is urging people to avoid contact with them.

"People can get infected with the deadly lyssavirus if scratched or bitten by a bat, so steer clear of bats at all times," Hunter New England Public Health physician Dr David Durrheim said.

"If not prevented, lyssavirus infection progresses to a rabies-like illness which is almost always fatal."

While the cause of the current deaths was unknown, HNELHD said mass fatalities among the animals usually occurred following heatwaves or when food was scarce, and they expected the deaths would continue throughout the summer.

Dr Durrheim warned people to avoid handling the animals unless they were appropriately vaccinated, trained and wearing the right protective clothing.

"Most people scratched or bitten by bats have been trying to rescue them," he said.

"It is essential that people do not touch bats as there is always the possibility of being scratched or bitten and being infected.

"Always assume that all bats and flying foxes are infectious."

You may also like:

While Dr Durrheim admitted human infection from Australian bat lyssavirus was very rare and could only be transmitted to humans when infected flying fox saliva came into contact with human tissue through an open wound or mucus membrane, he said it had proved deadly in the past.

Three previous cases of Australian bat lyssavirus in humans have been recorded - in Queensland in 1996, 1998 and 2013 - and all three resulted in death.

Dr Durrheim said anyone who found a sick or injured bat or flying fox should contact their local wildlife rescue group.

"If you see a bat in distress, injured or on the ground, do not try to rescue it," he said.

"You may put yourself at risk, and also cause more harm to the bat."

He also provided first aid advice for anyone who had been bitten or scratched by the animals.

"If someone is bitten or scratched by any type of bat they should thoroughly clean the wound for at least five minutes with soap and water immediately, apply an antiseptic such as Betadine and seek urgent medical advice," he said.

"If your pet has interacted with a bat, seek prompt assistance from your local veterinary practitioner."

Residents in the Manning-Great Lakes can contact FAWNA Wildlife Rescue on 6581 4141 if they find a sick or injured bat or flying fox.

Stay ahead with local news by signing up for the Great Lakes Advocate newsletter here.