Key Points
- Legionnaires’ disease is a severe form of pneumonia caused by the Legionella bacteria.
- Legionnaires’ disease is treatable with antibiotics.
- People can contract Legionnaires’ disease by inhaling mist containing Legionella bacteria. In general, it isn’t spread person to person.
Legionnaires’ disease isn’t something most people think about every day—but knowing the basics can help you protect yourself and others.
What Is Legionnaires’ Disease?
It’s a type of pneumonia (lung infection) caused by breathing in tiny droplets of water that contain Legionella bacteria. You can’t catch it from another person—only from contaminated water sources.
Where Does It Come From?
Legionella bacteria grow best in warm water. Common sources include:
- Air-conditioning systems in large buildings
- Hot tubs and spa pools
- Decorative fountains
- Hot water tanks and heaters
- Plumbing systems in hotels, hospitals, and apartment blocks
When water droplets from these systems become airborne, people nearby can inhale them.
Who Is At Risk?
Anyone can get it, but the risk is higher for:
- Adults over 50
- Smokers
- People with chronic lung disease
- Those with weakened immune systems
History Of Legionnaires Disease
“A review of the history of the infection known as Legionnaires’ disease reveals that it can be traced back as far as 1976, to a convention of the American Legion (a veterans association similar to the British Legion) in Philadelphia in America. While the reason for the convention was supposed to be a celebration of the 200th anniversary of America’s position as an independent nation, it would be remembered for entirely different reasons. Just one day into the convention, people in attendance began to be taken ill with symptoms not unlike those of pneumonia. Many of those at the convention were members of the American Legion, and by the end of the outbreak, 29 members of the Legion had lost their lives. In total, 34 were confirmed to have died from the illness while 221 in total had become ill. Of course, the Legionella bacterium existed long before 1976. However, it was the outbreak in Philadelphia that led the illness associated with it to be called Legionnaires’ disease after the American Legionnaires’ it affected. Furthermore, the same bacterium was confirmed to be the cause of the illness, and of an earlier outbreak of Pontiac fever that had developed in 1968. That fever was so-called because it broke out in Pontiac in Michigan.“Source: Legionella Control
Symptoms To Watch For
Legionnaires’ disease usually starts 2–10 days after exposure.
Common signs include:
- Fever, chills
- Cough (dry or producing mucus)
- Shortness of breath
- Muscle aches
- Headaches
- Sometimes diarrhoea, nausea, or confusion
If you notice these symptoms—especially after staying in a hotel, hospital, or using a spa—see a doctor quickly.
Treatment
It’s treated with antibiotics, and early treatment is key to recovery. Most people recover fully, but it can be serious and even life-threatening, especially in high-risk groups.
Prevention
You can’t always control large building water systems, but you can:
- Make sure hot tubs and pools you use are properly maintained
- Keep home water heaters at safe temperatures (above 60°C / 140°F)
- Report any poorly maintained fountains or spas to authorities
Bottom line: Legionnaires’ disease is rare, but it’s preventable with good water system management and quick medical attention if symptoms appear.
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What Is Legionnaires’ Disease?
