There are now nine confirmed cases of Legionnaires' disease from an outbreak in the Melbourne city area, following the release of information last Friday.
The Department of Health & Human Services is carrying out testing and investigations to determine any link to cooling towers in the south eastern area of Melbourne's Central Business District.
Victoria's Deputy Chief Health Officer, Dr Brett Sutton, said the six men and three women all report working in or visiting the CBD in the days before they became unwell. All showed the first signs of their illness between February 6 and 18, but the most recent six have only come forward or been identified since the release of information.
They are aged between 49 and 79 and are all current or former smokers - a high-risk category for acquiring Legionnaires' disease.
Most of the patients are recovering after receiving hospital treatment, including two who received intensive care.
Dr Sutton said the area south of Bourke St, between Queen and Spring Sts, was being investigated to try and find a common source.
"People who have visited the CBD between late January and mid-February and who may be suffering from pneumonia or flu-like symptoms should see their GP, who will assess the need for testing for Legionnaires' disease," Dr Sutton said.
"The Department is continuing to investigate these cases to seek to identify the possible source of their illness."
Dr Sutton said 74 cooling towers in the target area have already been tested, with an additional 34 being progressively sampled and disinfected.
Legionnaires' disease causes flu-like symptoms such as headache, fever, chills, muscle aches and pains, followed by respiratory problems and pneumonia developing over three or four days. The onset can be up to 10 days after the initial contact with the bacteria.
High risk groups in the community are people aged over 50, heavy smokers, heavy drinkers, people with diabetes or chronic lung disease and those with lowered immunity.
Legionnaires' disease infection is acquired through breathing in very fine droplets of water which contain the bacteria, such as spray drifts which are vented off from a contaminated cooling tower. Thorough management, decontamination and cleaning of affected towers is highly successful in eliminating risk.
The Legionella bacteria occurs naturally in the environment, mainly in water and soil. It is normally in very low concentrations but can increase markedly, particularly in man-made aquatic environments with warm recirculating water, such as air conditioning cooling towers.
Reviewed 28 February 2018