QUEBEC - Public health authorities say they have identified the source of Quebec City's outbreak of legionnaires' disease: an office building in the provincial capital.

They say samples taken from a cooling tower in a building on St-Joseph Street in Quebec City's lower-town area match the shape of legionella bacteria found in patients who've been treated.

Public health officials told a news conference today that the tower is safe again and there's no reason for people to modify work or leisure activities.

They say their conclusion is based on preliminary information released by the laboratory conducting the tests.

From the start, the source of the outbreak was suspected to have been an office cooling tower. Authorities scrambled to ensure all the towers were cleaned in the affected areas, while at the same time seeking to pinpoint the actual origin.

Since the outbreak began in July, 180 cases have been reported. Thirteen people have died.

The deadly bacteria grows in the stagnant water of cooling systems and spreads in little droplets through air conditioning.

While authorities haven't ruled out other buildings, they say the tower on St-Joseph Street played an important role in the outbreak in that city.

Authorities say the illness has been brought under control because they have disinfected the cooling systems in more than 100 buildings in the area.

Related on HuffPost:

Loading Slideshow...

  • The Name

    Legionnaires' disease" got its name from the unfortunate delegates who became infected during an outbreak at an American Legion of Pennsylvania convention. Thirty-four people died.

  • It's A Type Of Pneumonia

    Legionnaires' disease, a severe pneumonia, is one of two distinct illnesses associated with the Legionella genus.

  • Linked To Wet Environments

    Legionella bacteria are found in water sources, and can survive for several months in an aquatic environment - especially in warm water or when algae and organic matter are present. The bacteria may also do well in household devices, particularly those that produce mist -- shower heads and humidifiers, for instance.

  • Cannot Spread From Person To Person

    People may become ill if they inhale steam or mist containing the bacteria that causes legionnaires' disease, but they cannot pass an infection on to others. More recent research suggests that Legionella microbes may enter the lungs if someone chokes while eating or drinking, thereby allowing fluids and particles to enter the lungs instead of the stomach.

  • Starts With A Headache

    The Canadian Centre for Occupational Health and Safety notes that the first sign of legionnaires' disease is usually a headache accompanied by pain in the muscles and "a general feeling of unwellness." These symptoms may be followed by high fevers, shaking chills, coughs, fatigue, loss of appetite, nausea, diarrhea, hallucinations and more.

  • Older, Less Healthy People At Risk

    Not everyone who is exposed to the bacteria develops legionnaires' disease. People under age 20, for instance, are much less vulnerable. Middle-aged and older people are at greater risk, as are smokers. People who have diabetes, a weakened immune system and/or a chronic lung or kidney disease are also at increased risk when exposed to the bacteria.

  • Usually Not Fatal

    The majority of those infected survive, although their recovery can take several weeks. About five to 15 per cent of known cases have been fatal. The odds of recovery depends on many variables, such as age and overall health, as well as the timeliness of medical treatment.