In July 1976 a previously unknown bacteria killed 34 out of the 221 people that it infected during US bicentennial celebrations in Philadelphia. This new type of pneumonia kept scientists at work until approximately 6 months later when the bacteria was isolated and named legionella. Legionnaire's disease was the name given to the pneumonic infection caused by legionella.

This year an outbreak of Legionnaire's disease has been plaguing Quebec City since mid-July. The deaths of 11 people out of the 173 reported infections as of September 4th, 2012 have been startling citizens and officials. The figures may continue to rise although the rate has slowed within the last week. These numbers are currently more than double the normal rate of Legionnaire's disease infections in Canada. The Pathogen Safety Data Sheet for legionella on Canada's Public Health Agency website lists an average of 75 cases of Legionnaire's disease annually for the entire country.

This is the second largest outbreak of Legionnaire's disease in Canada's history. The largest occurred in Toronto during the summer of 2005 and claimed the lives of 21 out of the 127 people who were infected. One factor that sets this outbreak apart is the uncertainty surrounding the source of the infection. Another is the failure of a government plan of action created in 1997 to prevent such an outbreak.

Legionnaire's disease is not contagious. L. pneumophila is the species that is responsible for 61%-88% of the Legionnaire's disease cases in Canada but other rare species can sometimes be the cause. The legionella responsible for an infection enters the body through the inhalation of contaminated water vapour. If the person who has inhaled the water vapour containing suspended legionella is susceptible to infection they will begin to show symptoms after an incubation period of 2-14 days. Other people who inhale legionella are either not susceptible to infection or will develop Pontiac fever.

Both Pontiac fever and Legionnaire's disease are considered legionellosis. Those with Pontiac fever will usually become ill and recover within 2-5 days of infection and do not require antibiotics to recover. No deaths have been reported from a case of Pontiac fever.

Legionnaire's disease occurs when legionellosis becomes pneumonia in the lungs and is much more serious. Antibiotics are necessary for recovery from Legionnaire's disease and are not always effective. Canada reports a 15%-25% mortality rate among cases of Legionnaire's disease.

A wide range of symptoms can indicate Legionnaire's disease. Headache, muscle pain, fever, and chills are the first symptoms. As the infection continues to develop, the host may experience fatigue, coughing, shortness of breath, nausea, vomiting, diarrhea, loss of appetite, and mental changes. Those most susceptible to Legionnaire's disease are middle aged to elderly people, especially those who are heavy smokers or have chronic lung problems, and people with compromised immune systems.

Legionella is a very common bacteria in nature. It lives in lakes and ponds and is dormant until the temperature reaches 20 degrees Celsius (68 degrees Fahrenheit). When the temperature rises above that level legionella can grow until the temperature reaches 50 degrees Celsius (122 degrees Fahrenheit). The preferable growth environment is in stagnant water between 25 and 45 degrees Celsius (77-113 degrees Fahrenheit).

When legionella find these ideal growth ranges in man-made environments it is inevitable for humans in the area to breath in contaminated water vapour. Cooling towers, misters in grocery stores, hot tubs, water fountains, large plumbing systems, and parts of air conditioning units for large buildings are only some man-made environments where legionella can thrive and infect people. Conditions become especially hospitable to legionella during mid to late summer in Canada.

The Toronto outbreak was limited to one senior living facility. This made it simple to isolate the source of the contaminated water to the building's cooling tower. Victims of the current outbreak are not limited to one building. There is a possibility that the cooling systems of two specific buildings in Old Quebec are responsible for the outbreak. Authorities are still trying to narrow down other possible sources of contaminated water vapor common to those currently infected with Legionnaire's disease while water samples from the suspected cooling systems are tested.

Cooling systems from over 100 other buildings are also being tested. Samples were collected before water in the cooling tanks was disinfected. Citizens of Quebec City are left wondering why these measures were not already being taken to prevent a Legionnaire's disease outbreak of this magnitude. A government report in 1997 recommended the creation of a registry of buildings with ventilation systems that use cooling towers in order to quickly isolate outbreaks. This registry could have been used to implement tougher regulations for inspecting and disinfecting such cooling towers as well but it was never created. The tragic results of such procrastination have spurred the current administration into action.

Results from the tests on these cooling systems are expected by mid-September. Authorities are becoming confident that the outbreak is now under control as the rate of new cases appearing has slowed.

Quebec City is not alone in its struggle with Legionnaire's disease this year. Outbreaks have been reported in Chicago (United States), Edinburgh (Scotland), Auckland (New Zealand), Stoke-on-Trent (England), and Calp (Spain). While Quebec City's outbreak has not had the highest death rate so far they have experienced the highest amount of infections.

Author: +Duncan Hollis