More than 140 people have been bitten or scratched by bats in New South Wales so far this year, putting them at risk of a rabies-like disease.

What is rabies and Australian bat lyssavirus? Rabies virus and Australian bat lyssavirus (ABLV) belong to a group of viruses called lyssaviruses

Rabies virus and Australian bat lyssavirus (ABLV) belong to a group of viruses called lyssaviruses These viruses are usually transmitted via a bite from an infected ("rabid") animal

These viruses are usually transmitted via a bite from an infected ("rabid") animal They all cause a similar illness known as rabies, which affects the central nervous system and is usually fatal Source: NSW Department of Health

All have been treated with a preventative course of vaccines to try to stop them contracting the lyssavirus.

New South Wales Health is urging people to treat every bat as if they carry the fatal disease because it was unclear "which bats have the infection".

The department advised anyone who came into contact with a bat to see their doctor immediately.

"Everyone who gets bitten or scratched by a bat in Australia should have the preventative treatment," NSW Health's director of communicable diseases Dr Vicky Sheppeard said.

"If the infection does develop then it is too late to do anything to cure it once the infection starts."

Flying foxes migrate from one end of Sydney to the other in the evening. ( Supplied: Peggy Eby )

Three people have died from lyssavirus, between 1996 and 2013, and all have been from Queensland.

The vaccine includes a course of four shots over a month and is free.

NSW Health expects the number of people to be bitten or scratched by bats to reach 200 by the end of the year because this month is local breeding season.

"This is the time when bats are birthing their pups and people do tend to find them on the ground and try to help them," Dr Sheppeard said.

"But they must remember they shouldn't handle any bat."