An illustration of Legionella pneumophila bacteria, the cause of Legionnaires' disease. (File photo) Photo: AFP/ Science Photo Library - Kateryna Kon
Two people have died from legionnaires' disease in Melbourne, with health authorities still yet to identify a source of an outbreak that has left dozens of people in hospital.
Victoria's chief health officer confirmed a man in his 60s and a woman in her 90s died from the disease. And the number of cases in Melbourne has grown to 77, of whom 75 people have required hospitalisation.
But Chief Health Officer Clare Looker said on Sunday morning the outbreak could be slowing.
"We've definitely seen a decrease in the speed with which notifications are coming in and definitely a clustering of those symptoms and onsets from those earlier dates," she said.
"Hopefully we're seeing the tail of things."
Health authorities narrowed down the likely source of the outbreak to water cooling towers on industrial buildings in the suburbs of Laverton North and Derrimut.
Testing had been carried out on 54 of around 100 cooling towers in the area and health authorities had requested the latest test results from the operators of about 1000 cooling towers across Melbourne.
Dr Looker said the slowing rate of new cases suggests the source of the outbreak might already have been neutralised.
"There may have been colonisation of a unit that then subsequently cleared," she said.
"(It may have) contributed to the infection of individuals and then cleared, either through the normal processes of the machinery or passing through the system."
Authorities warn people who have been in Melbourne and have symptoms
Legionnaires' disease is caused by the Legionella bacteria, which can be found in natural bodies of water such as lakes and hot springs, as well as spas and some water cooling systems.
Authorities are urging anyone who has visited Melbourne since mid-July to seek medical advice if they have the symptoms of a chest infection alongside a fever, chill, cough and headaches.
The disease is not spread by person-to-person transmission and authorities have been working to determine the source of the current outbreak.
This outbreak is the largest since an outbreak of 125 cases at Melbourne Aquarium in 2000.
- This story was first published by ABC