As bat breeding season takes off in NSW, the state's health authority has issued a warning about contracting the mammal's potentially fatal lyssavirus.

The peak NSW health authority has issued a warning over the deadly disease risks posed by bats as their breeding season takes-off.

Four bats infected with the potentially fatal lyssavirus have already been recorded in NSW this year, according to NSW Health's Dr Vicky Sheppeard.

When passed to humans, the rabies-like illness lyssavirus can prove fatal if not treated.

"During the bat birthing season in October and November, we find people are more likely to come in contact with bats, as young and miscarried pups may be on the ground, prompting people to pick them up or attempt to rescue them," Dr Sheppeard said in a statement on Monday.

"People should 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."

This year alone, 142 people in NSW have been given rabies treatment after they were bitten or scratched by a bat.