History of Legionnaires ' disease
What is Legionnaires' disease ?
In 1976 an outbreak of lung infection (pneumonia) occurred among American legionnaires
(ex-servicemen) who attended a conference. 221 people developed pneumonia, and
34 died. A germ (bacterium) that had never been identified before was found to
be the cause and was named Legionella pneumophila (pneumophila means loving the
lungs). Since then, many different types of legionella bacteria have been identified.
Legionella bacteria live in fresh water and mud and are found all over the world.
How do you get Legionnaires' disease ?
The source of the germs (bacteria) in an outbreak is usually a man-made water
distribution system where the bacteria have multiplied in great numbers. Warm
storage tanks where the water stagnates are ideal for legionella bacteria to multiply.
The bacteria thrive in water temperatures between 20°C and 45°C - about
35°C is the optimum temperature. This means that Legionnaires' disease can
be caught from:
Infection of legionellosis is caused by breathing in (inhaling) water droplets
(aerosol) that are contaminated by many legionella bacteria. An outbreak can affect
many people in the same hospital, hotel, office complex or other large building,
around the same time. However, they do not infect each other - they all acquire
the disease from the same place. It cannot be acquired by drinking infected water,
only by inhaling droplets which allow the bacteria to reach the lungs directly.
- Piped water, especially hot water, in buildings where long runs of pipe work
can be a source of the bacteria.
- Circulating water droplets in air-conditioning and cooling systems, cooling
towers and evaporative condensers.
- Whirlpool spas (jacuzzis), other warm-water baths and shower heads.
- Decorative fountains.
- Nebulisers and humidifiers (including some types of breathing equipment) if
topped up with contaminated tap water
Risk factors for developing Legionnaires' disease
Not everyone exposed to legionella bacteria becomes sick. You're more likely to
develop the infection if you:
Legionnaires' disease is a sporadic and local problem in hospitals and nursing
homes, where germs may spread easily and people are vulnerable to infection.
- Smoke. Smoking damages the lungs, making you more susceptible to all
types of lung infections.
- Have a weakened immune system as a result of HIV/AIDS or certain medications,
especially corticosteroids and drugs taken to prevent organ rejection after a
- Have a chronic lung disease such as emphysema or another serious condition
such as diabetes, kidney disease or cancer.
- Are 50 years of age or older.