Legionella bacteria has been found in cooling towers at St George Hospital.
A routine check of the hospital's cooling towers on November 29 tested positive for Legionella bacteria.
Cooling towers at an office building in the Kogarah business area had positive results to Legionella bacteria on December 2.
An investigation examining whether there are any common factors between the two locations is underway.
The cooling towers have since been thoroughly cleaned and decontaminated, Professor Mark Ferson, Director, Public Health Unit, South Eastern Sydney Local Health District said.
No human cases of infection have been linked to the cooling towers and experts advise that the risk of infection to anyone is low.
The cooling towers at the Kogarah office building were also immediately cleaned and decontaminated and Georges River Council was notified.
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.
Routine testing of cooling towers helps identify contamination early and allows for prompt cleaning and corrective actions.
In 2016 a cluster of cases of Legionnaires' disease occurred in Kogarah and three people were treated for legionnaires' disease at St George Hospital.
All three had been in the vicinity of Kogarah shops and businesses.
At the time the public health unit was notified that a cooling tower at the hospital could be the source of the outbreak.
The tower had returned a positive result for legionella after a monthly routine check.
It is believed there are up to nine cooling towers in the area.
Last year, NSW Health strengthened the Public Health Regulation to reduce the community's risk of Legionnaires' disease, requiring building owners to conduct risk assessments and monthly tests on cooling towers and notify high levels of Legionella and other bacteria to local councils.
Legionnaires' disease is an infection of the lungs (pneumonia) caused by legionella bacteria, which are commonly found in bodies of water. It cannot be spread from person to person.
The incubation period between exposure and development of symptoms is two to 10 day 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.
It is serious infection that may be life-threatening, particularly in the case elderly people.
People who develop this disease are diagnosed by chest X-ray and a urine test and usually require antibiotic treatment in hospital.
Outbreaks of the disease are most frequently linked to contaminated water cooling systems of air conditioning plants in large buildings.
For more information about water cooling systems management contact your local Public Health Unit on 1300 066 055 or go to health.nsw.gov.au
Details on Legionnaires' disease click on this fact sheet.