SYDNEY - Australia's New South Wales (NSW) health authorities on Thursday issued a warning to residents and visitors in southern and western NSW, telling them to take extra precautions to avoid mosquito bites after the detection of the mosquito-borne Murray Valley Encephalitis virus (MVE) in the state.

The MVE virus has been detected in sentinel chickens near Leeton, Hay and Moama in southern NSW and in the Macquarie Marshes in the west of the state, NSW Health said.

NSW Health Director of Health Protection Jeremy McAnulty said the latest detections should serve as an important reminder for people to protect themselves.

"The important message is to avoid mosquito bites and be alert to any symptoms," McAnulty said in a statement.

"While MVE is relatively rare, and most people will not develop symptoms, it is a serious mosquito-borne disease," McAnulty said.

"In mild cases, symptoms of MVE include fever, headache, nausea and vomiting and muscle aches. In more severe cases symptoms can include neck stiffness, lethargy, drowsiness, confusion, delirium, tremors, neurological problems and coma in severe cases."  

The MVE virus is transmitted by infected mosquitoes which breed in flooded, grassy and swamp areas and around rivers and waterways.

According to NSW Health, the current area of risk for MVE extends in regions west of the Great Dividing Range and people living around rivers and wetlands and in recently flooded areas in western NSW are at the highest risk of catching the mosquito-borne disease.