The second person this year has died from Legionnaires' disease in Sydney, and health authorities are dealing with a new outbreak in the city's inner west.

An elderly Sydney patient has died from Legionnaires' disease, and authorities are dealing with a new outbreak in the city's inner west.

NSW Health would not confirm if the death, the second in the city from the lung infection this year, was linked to an outbreak in the CBD.

The patient died last week at Concord Hospital, a NSW Health spokeswoman told AAP.

The death comes as three cases in the Burwood area are being investigated by Sydney Local Health District's Public Health Unit.

It's working with Burwood Council to investigate all cooling towers in the area, a statement from the NSW Department of Health said on Tuesday.

The cases are not related to a recent outbreak in Sydney's CBD, which has resulted in five people being treated.

The bacterial lung infection causes fever, chills, a cough and shortness of breath.

Middle-aged and older people, particularly smokers or people with chronic lung disease, are most at risk.

Last week, Dr Vicky Sheppeard, director of the communicable diseases branch at NSW Health, said five of the 89 cooling towers and areas tested in the CBD for the potentially deadly bacteria had returned positive results during preliminary testing.