What you need to know about legionnaires’ disease
A large grouping of Gram-negative Legionella pneumophila bacteria are shown in this colorized 8000X electron micrograph image from 2009. (AP / Janice Haney Carr)
Published Monday, August 27, 2012 3:00PM EDT
Last Updated Tuesday, August 28, 2012 11:42AM EDT
An outbreak of legionnaires' disease in Quebec City has killed eight people and sickened more than 100, making it one of the deadliest outbreaks of the disease in Canada in 25 years.
While officials say they think they now have the month-long outbreak under control, there could be more cases to come. That’s because the disease typically incubates for two to 10 days before it starts causing symptoms and many of those infected recently might still be undiagnosed.
What is legionnaires’ disease?
Legionnaires' disease is caused by water-borne bacteria breathed into the lungs through tiny droplets, leading to pneumonia.
Legionella bacteria are always present at low levels in water. But in warm conditions, the bacteria can multiply to dangerous levels. They tend to grow in the stagnant water of cooling systems and humidifiers during heat waves and then spread through the air system via droplets.
The disease can also spread through mist from public showers and hot tubs and in other warm, humid, and poorly ventilated areas. Even drinking water fountains and indoor decorative fountains have been linked to legionnaires' outbreaks.
The disease cannot spread person-to-person.
What is causing this outbreak?
The source of the outbreak in Quebec City is believed to be air conditioning cooling towers on the roofs of two buildings in the city. Authorities say they have disinfected 89 cooling towers and believe that the outbreak has been contained, though more cases could still be diagnosed.
Why is the disease called legionnaires?
Legionnaires' disease was first identified during an outbreak at a Philadelphia convention of the American Legion veterans' organization in 1976 that killed 34 people.
When conventioneers started becoming sick with a mysterious pneumonia that caused fevers topping 107 degrees, a team of 20 infectious disease experts from U.S. CDC were flown in to investigate. Six months later, they discovered a never-before-seen bacterium in the hotel’s air-conditioning system and named it Legionella pneumophila.
Since then, more that 35 Legionella species that cause disease and several subtypes have been identified.
How dangerous is the illness?
While not everyone who breathes in Legionella-infected droplets will become sick, the bacteria can infect the lungs and cause a form of pneumonia called legionellosis which results in a persistent and sometimes bloody cough, shortness of breath and chest pains.
Most healthy people can be treated successfully with antibiotics. But the elderly, people with weak immune systems, and heavy smokers are most at risk of serious complications. They can develop a serious infection that causes a persistent fever, difficulty breathing, and sometimes death. The illness is fatal in five to 30 per cent of cases.
In this outbreak, the average age of those who have died is 79.
A milder infection caused by Legionella bacteria is called Pontiac Fever. While it causes fever, headaches, and muscle aches, it doesn’t cause pneumonia. That illness lasts for 2 to 5 days and symptoms go away on their own without treatment.
How can it be prevented?
Legionnaires’ disease is not common, and the risk of getting it is generally low.
It’s hard to minimize your risk in large buildings, such as hotels and hospitals, since there is no way to know if the bacteria are present in air systems. Building managers and maintenance staff can control the risk of infection from these sources through good engineering and proper ventilation design, as well as good infection control policies and guidelines.
In your home, you can minimize risks through the proper maintenance of all mist-producing devices, such as humidifiers, vaporizers, hot tubs, and whirlpools.
Clean and disinfect these devices regularly according to the manufacturers' directions. And always empty humidifiers and vaporizers after you turn them off, adding clean or distilled water when you are ready to use it again.