Two people living in Melbourne's southeast have contracted Legionnaires' disease, with health authorities urgently working to find the source.
The cases have been identified in Cranbourne East, Victoria's acting chief health officer Mihaela Ivan said in an alert issued on Wednesday.
Both people developed symptoms earlier in August and required treatment in hospital.
Investigations are under way into potential sources of the outbreak, including local cooling towers, pools and spas.
Healthcare workers are encouraged to look out for Legionnaires' disease in people with flu-like symptoms who've been in Cranbourne East since the beginning of August and to "consider alternative diagnoses to COVID-19 for respiratory infections and undertake appropriate investigations".
Legionnaires' is a type of pneumonia caused by legionella bacteria, which can be found in natural bodies of water like lakes, rivers, creeks and hot springs.
It can also be found in spas, potting mixture, warm water systems and artificial cooling or heating systems.
The disease does not spread from person to person or by drinking contaminated water, it is contracted by breathing in fine droplets of water containing the bacteria.
Those most at risk of catching the disease are people aged over 50, those with weak immune systems, chronic lung disease, or who smoke and drink heavily.
Some symptoms of the disease are similar to COVID-19, since it can present as flu-like with headaches, a fever and a cough. The illness could progress to pneumonia, with some sufferers experiencing confusion.
Anyone with these symptoms who works, visits or lives in the Cranbourne East area is urged to seek immediate medical attention.
Early diagnosis and treatment with antibiotics can reduce severity of illness and complications.
