An outbreak of Legionnaires' disease possibly linked to building cooling towers in Melbourne's CBD is being investigated by health authorities.
Five people – three men and two women, aged from 51 to 71 years – were recently hospitalised after contracting the pneumonia-like condition.
Authorities are disinfecting and sampling 92 systems in buildings between Spring and Elizabeth streets in the city's east, to minimise risk while they search for the source.
Victoria's Deputy Chief Health Officer, Dr Finn Romanes, said the Health Department began investigating links to CBD cooling towers after interviews with those affected last night and Wednesday morning.
They all reported working in or visiting the eastern end of the CBD in the days before they became ill. They started feeling sick within the last week of March and the first week of April, Dr Romanes said.
All five have been discharged and are recovering. One of them had required life support in an intensive care unit.
Authorities have sampled and disinfected three workplaces linked to the people infected. They identified the further 89 potentially linked water systems by tracing the movements of all five who fell ill.
"It's safe and appropriate to come to the central business district for work and leisure," Dr Romanes said. "We are taking this as a precaution to minimise any risk that might be present.
![Legionella pneumophila bacteria.](/web/20170413114841im_/http://www.theage.com.au/content/dam/images/g/v/j/u/h/i/image.related.articleLeadwide.620x349.gvjnjn.png/1492069439575.jpg)
"My message to people who have visited the CBD between late March and earlier this month and who may be suffering from pneumonia or flu-like symptoms is to visit their GP who will assess the need for testing for Legionnaires' disease."
The infection is acquired by breathing in fine droplets of water which contain the bacteria, such as spray drifts which are vented off from a contaminated cooling tower.
![Legionnaires' disease, a life-threatening form of pneumonia caused by the bacteria legionella, is not contagious.](/web/20170413114841im_/http://www.theage.com.au/content/dam/images/g/p/1/2/o/p/image.related.articleLeadwide.620x349.gvjnjn.png/1491991328290.jpg)
Leading plumbers in Victoria say they have been warning authorities about a heightened risk of legionella and biohazards in high-rise buildings in Melbourne for at least 18-months.
Plumber and gas fitter Ian Pewtress said he raised concerns with VicHealth's specialist legionella unit in late 2015, but was told it was a Victorian Building Authority (VBA) issue.
Mr Pewtress said a legionella working group was mooted by the building authority in September, but nothing had happened since.
"The VBA was asked about it in a stakeholder meeting in February and the reply given was that biohazard controls was not a high priority," he said.
Last year Fairfax Media reported the VBA took nine months to demand a solution for a legionella risk in the warm-water system of North Melbourne's George apartments.
Dr Romanes said Victoria had a "rigorous regime" for managing the risk of the legionella in water systems.
"We've got one of the toughest regimes in the world, recently picked up by New York," he said. "We have a maintenance system and we have an inspectorate and audits and compliance checks."
In Sydney, 15 people fell ill due to two separate outbreaks - in March and May 2016 - linked to two water cooling towers. One man - aged in his 80s died after contracting the infection.
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.
Those most at risk are people aged over 50, heavy smokers, heavy drinkers, people with diabetes or lung disease; and those with lowered immunity. It can take 10 days after initial contact for a person to start feeling unwell.
So far this year 26 people have contracted Legionnaires' disease compared to 21 for the same period last year, according to Health Department data. In Victoria each year there are between 70 to 80 cases of Legionnaires' disease.
The bacteria occurs naturally in the environment, mainly in water and soil. It is normally in very low concentrations but can increase dramatically, particularly in man-made aquatic environments with warm recirculating water, like air conditioning cooling towers.