MONTREAL -- Montreal public health is investigating a possible legionella outbreak in the city's LaSalle borough. 

Seven cases were declared among the population between Sept. 9 and 22, and an investigation is underway to determine the cause of the outbreak -- including cooling towers and other parts of the water system. A team is located south of the aqueduct canal that brings river water to the Atwater purification plant. 

Every year, about 50 Montrealers contract Legionellosis, a respiratory infection that can be caught by breathing in fine droplets of water contaminated by the legionella bacteria. The bacteria can also be found in hot tubs, baths, electric water heaters, home humidifiers and respiratory treatment equipment. 

"Legionnaires’ disease is not a common disease and, for people in good health, the risks of getting it are quite low," Montreal public health's website reads. "Legionnaires' disease does not spread from person to person." 

Symptoms of Legionnaires' disease include high fever, chills, cough, fatigue, muscle pain and loss of appetite. Those most at-risk are people aged over 50, smokers, heavy drinkers, people with chronic diseases, people with weakened immune systems and people who've recently undergone surgery. 

In the summer of 2012, an outbreak of Legionnaires' disease caused by cooling towers left 14 people dead and 164 sick in Quebec.