​NSW Health continues to advise people who have been in the Sydney CBD area in the past two weeks to be on the lookout for symptoms of Legionnaires' disease as a sixth case of the disease has now been identified in a person who spent time in the area.

Five cases of Legionnaires' disease were reported in a public health alert on Thursday May 26, all in people who had also spent time in the CBD area.

While no single source of the cases has been identified, and it is possible the cases are unrelated, NSW Health environmental health officers have worked with the City of Sydney to inspect and sample 124 high priority cooling towers in the area.

Additionally, owners of six towers have been directed to undertake immediate measures to rectify identified defects. Microbial sampling results are expected later this week, to determine if any of these towers are a potential source of the infection.

All six people have been identified with the 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 the cooling system are emitted into the air and breathed in.

The six people, two women and four men ranging in age from their 40s to 70s, independently visited locations between Elizabeth Street, Clarence Street, Park Street and Martin Place in the 10 days prior to their onset of symptoms. All six people were admitted to hospital for treatment of their pneumonia, with one person now discharged.

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.

People who develop Legionnaires' disease are diagnosed by chest x-ray and a urine test and usually require antibiotic treatment in hospital.

Routine testing of cooling towers helps identify contamination early and allows for prompt cleaning and corrective actions. Legionnaires' disease cannot be spread from person to person.

Building owners must ensure that their cooling towers are well maintained and that they are compliant with the requirements of the Public Health Regulation 2012.

Public health units in local health districts across NSW follow up every case of Legionnaires' disease and work closely with local councils in the management of cooling towers.

For more information about water cooling systems management contact your local Public Health Unit on 1300 066 055 or visit Legionella control.

For more information on Legionnaires' disease see the Legionnaires' disease fact sheet.