In Quebec, health officials are trying to find the source of an outbreak.
Ontario health officials say a seasonal increase is expected in August and September. Between Aug. 1 and Sept. 11, the province had 59 confirmed cases of legionellosis, compared with the five-year average of 18 or 19 cases in August between 2007 and 2011.
"The increase in legionellosis cases reported within Ontario is likely due to a number of complex and interdependent factors, including better awareness and more extensive testing," Dr. Doug Sider, associated chief medical officer of health for Ontario, told CBC News in an email.
Legionnaires' disease is a severe pneumonia. People can fall sick if they inhale steam or mist containing the bacteria that causes the illness, but no one has been known to pass on the infection to others, the Public Health Agency of Canada said.
"You may find legionnaires' bacteria in people's pipes at home, and buildings, air conditioners, fridges, water tanks, everywhere," said Dr. Michael Gardam, director of infection prevention and control at Toronto's University Health Network.
"But just because it's there doesn't necessarily mean it's making people sick."
Any standing water source can potentially contain the bacteria, including water fountains, hot tubs, fountains and even water sprayers used to keep vegetables wet in grocery stores.
It's only when the bacteria get aerosolized, or in the air, and sucked into the lungs that they can cause problems.
At Victoria General Hospital in Halifax, the bacteria have lurked in the water pipes since the mid 1980s. The hospital has resorted to a labour-intensive strategy to protect patients at high risk. Such patients aren't allowed to drink tap water, or draw their own baths and shower.
"It's a challenge, no question about that," said Dr. Lynn Johnston, head of infectious disease at Halifax’s Capital District Health Authority. "You can imagine when you first get up to brush your teeth, your first instinct is to go to a sink and not to a bottle of sterile water."
Victoria General first tried increasing the amount of chlorine in the pipes, but that was corrosive to pipes and caused floods. Super heating is another strategy but it poses burn risks to patients and needs to be done for every water tap in the building or the bacteria can regrow.
Now the Halifax hospital uses a different form of chlorine designed to get at the bacteria in biofilms — the guck that acts as protective environment for legionnella.
A new hospital building is in the planning stages.
In Quebec City, officials have disinfected downtown area cooling towers, which are the prime suspect in the outbreak, but they remain open-minded until final lab tests are completed in mid-October.
Cooling towers are a collection point for airborne contaminants, said Gary Sweeney of Cooling Tower Maintenance in Toronto. In the summer, air cooling systems are ideal for incubating the bacteria, he said.
Cooling tower maintenance
"It's a perfect breeding ground," said Sweeney. Cooling towers typically run at 95 to 100 F, about the same temperature range that labs use to grow bacteria.
Cooling towers should be cleaned every six months, but building mangers on a fixed budget may not keep up, Sweeney said.
"The cooling tower is on the roof," Sweeney said. "Most people don’t even know what it looks like, let alone maintain it. So it gets ignored until it becomes a catastrophe and then everybody focuses on it."
Tony Dickie, 59, of Truro, N.S., believes he contracted legionnaires' disease two years ago while inspecting ductwork.
"You lose all muscle tone," Dickie said. "I had several blood transfusions. The whole body went septic. From what I'm told, the family was called in the Sunday I went into the hospital and told I wasn't going to make it."
Dickie said he feels for the families affected in Quebec. He still has problems with memory and balance. He's lobbying the Nova Scotia government to require companies to clean and maintain water and cooling systems that might harbour the bacteria.
Isolated cases of legionnaires' disease occur all the time, health officials say. In previous outbreaks in Canada, the U.S., and Europe, the source was never found.
"If it's diagnosed in time, the antibiotics we use to treat regular community acquired pneumonia are very good for treating this," Gardam said.
In terms of prevention at an individual level, experts said the best defence is common sense measures like keeping water systems clean.