Wollongong residents are being urged to be on the lookout for symptoms of Legionnaires' disease after six confirmed cases in the last three months.
Further south, residents are also on notice with five cases in the Nowra / Bomaderry area in the past two weeks and an additional case which was notified this morning now under investigation.
Illawarra Shoalhaven Local Health District public health director Curtis Gregory said no specific source of transmission had been identified in any of the cases so far.
Outbreaks of the disease are most frequently linked to contaminated water cooling systems of air conditioning plants in large buildings.
"Legionnaires' disease is caused by a bacteria known as legionella," Mr Gregory said. "If not maintained properly, cooling towers can become contaminated with legionella.
"As the air blows through to provide the cooling mechanism, it will pick up the bacteria in an aerosol and that aerosol will disperse in a plume. If people are exposed to that plume outside the building, they can become infected.
"We've now completed inspections and sampling of around 40 cooling towers in the Wollongong LGA, and there's been no positive detections for legionella.
"And today we've conducted inspections of towers in the Nowra / Bomaderry area given the recent outbreak and are awaiting the results."
Mr Gregory said while the Wollongong cases did not appear to be linked, there did appear to be a link in the Shoalhaven cases.
"The Wollongong cases are quite dispersed - in time and location," he said. "With Nowra, they're clearly linked - they're much more tightly grouped together geographically and timewise."
Legionnaires' disease cannot spread from person to person and is not contagious. However it can cause severe respiratory symptoms, and can be life-threatening.
"There's flu-like symptoms such as fever, chills, a cough and shortness of breath, which may lead to severe chest infections and it can be fatal," Mr Gregory said.
"In the 1987 outbreak in Wollongong, around a dozen people died, but there were no fatalities during the 2005 outbreak in the city.
"So whenever we get elevated numbers, there are concerns which is why we move quickly to try and find the source."
Mr Gregory said the public health unit would continue to investigate the local cases and monitor for additional cases.
This would include working with council and businesses to ensure the routine testing of cooling towers to help identify contamination early, and ensure prompt cleaning.
"The public health unit urges businesses and building owners to ensure their cooling towers are operating and maintained properly and cleanly," he said.
An alert had also been issued to GPs and clinicians in the district about the possibility of cases of the disease, which is diagnosed by a urine test and treated with antibiotics.
"They may also be a climatic link as there's been an increase in numbers in other parts of the state as well," Mr Gregory said.
"Wet and humid weather is perfect for bacterial growth so an increase in cases towards the end of a warm, wet summer is not unusual.
"Cases could even come from a natural environmental source, like a water body or water feature."
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