Cooling towers across Melbourne are being disinfected in a bid to stem a growing outbreak of legionnaires' disease that has left several people in intensive care.
There are 33 confirmed cases and 10 suspected cases as of Tuesday afternoon but the number is expected to rise in coming days.
The source of the outbreak is yet to be confirmed and authorities are keeping an open mind, but Victorian Chief Health Officer Clare Looker believes it is likely to be a single cooling tower in Melbourne.
"We have some suburbs that have had more crossover of cases than others and these are really across the north and west of Melbourne," Dr Looker said.
"At this stage, we haven't been able to identify a single site that has been visited by all the cases."
The majority of patients admitted to hospital are male, aged over 50 and live or work in metropolitan Melbourne.
Six people were in intensive care on Monday.
Eighteen cooling towers at public venues, industrial sites and factories were being disinfected and many patients had visited several of the sites.
Mapping software has been used to identify places the cases visited or passed by during their incubation period.
Legionnaires' disease is caused by the legionella bacteria and tests indicate the outbreak is caused by legionella pneumophilia serogroup 1.
The bacteria is found in natural bodies of water as well as spas, warm water systems, potting mix and artificial systems that use water for cooling.
Anyone with symptoms has been urged to seek medical help immediately.
Those with underlying diseases, particularly people who are immunocompromised, elderly people and smokers are at greater risk of infection.
"The symptoms for legionnaires' are really similar to those of any pneumonia, so fevers, chills, respiratory symptoms, general aches and pains," Dr Looker said.
"I would really encourage anyone who's obviously experiencing any of those symptoms to visit their local doctor, or if they're very unwell, obviously, to call triple zero or to visit hospital."
