SYDNEY - Health authorities in Australia's New South Wales (NSW) said Wednesday that people who had been in the Sydney CBD area in the past 10 days are advised to be on alert for symptoms of Legionnaires' disease.

Seven people who have developed Legionnaires' disease, a severe form of pneumonia, had spent time in the area in the last three weeks, the NSW Ministry of Health said in a media release.

All seven people have been admitted to the hospital for treatment of pneumonia and have been identified with the Legionella bacteria that causes Legionnaires' disease, which is often associated with contaminated cooling towers of large buildings.

People can be exposed to the bacteria if contaminated water particles from a cooling system are emitted into the air and breathed in, the ministry said.

But Legionnaires' disease cannot be spread from person to person, it added.

Symptoms of Legionnaires' disease can develop up to 10 days from the time of exposure to contaminated water particles in the air and include fever, chills, a cough and shortness of breath and may lead to severe chest infections such as pneumonia.

Local environmental health officers are working closely with the City of Sydney Council to inspect cooling towers, the ministry said.