Legionnaires disease thrives in poorly-maintained air-conditioning towers.
It is an air borne disease and has an incubation period of up to 10 days after initial exposure.
Symptoms include headaches, fever, chills and muscle aches.
The deadly legionnaire disease outbreak occurred in the north of Melbourne. So far ten victims have been diagnosed with the disease.
A 51-year-old man was tested positive to the airborne disease and was admitted to the Austin Hospital.
He said that he had been working in the infected area, Preston and he lived in the northeast region of Melbourne.
Doctors say that he will soon be discharged from the hospital. Recently a 63-year-old man was diagnosed at Box Hospital.
The outbreak killed another victim in the Austin Hospital, Ron Dickins, 85, who was a reservoir man.
Another infected 83-year-old woman showed signs of recovery in the Austin Hospital and is expected to be discharged soon.
Despite the increase in the number of people being infected with the disease the infected tower that sparked the outbreak is yet to be identified.
The Department of Human Services said that people need not fear and have to return to the regular routine.
It also said that all towers in the Preston area had been cleaned and tests were carried out last week to make sure that there is no more contamination with the bacteria.
DHS spokesman Bram Alexander said that the results from the tests would be released soon.
He said that people have to resume that regular activity and should continue with their week as normal. Mr. Alexander said that all cooling towers have been disinfected.