Legionella bacteria and Legionnaires’ disease

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Legionella is a group of bacteria causing legionellosis, a collective name for over 40 illnesses caused by Legionella, two of which are the best known: a pneumonia-type illness called Legionnaires’ disease and a mild flu-like illness called Pontiac fever. Legionnaires’ disease takes its name from a legionella outbreak amongst veterans in Philadelphia in 1976, which led to the discovery of the disease. Most people do not fall ill after exposure to the legionella bacteria. In some cases, you can get mild flu-like symptoms. In the most serious case, infection can lead to severe pneumonia. This is Legionnaires’ disease.

How do you catch it?

The legionella bacterium (legionella pneumophila) occurs naturally in water and soil. You can get sick trough breathing in the bacteria. However, drinking contaminated water is harmless. Legionella typically does not spread directly between people. The incubation period of the bacteria can vary from two to twenty days, but is usually five or six days. Legionella bacteria can grow rapidly in warm and stagnant water (and thrive at a temperature of 25 to 45 degrees Celsius). If the water is being sprayed, you can breathe in tiny droplets and become infected. Think of showers, a garden hose or a hot tub. You can also become infected through cooling towers that use water to cool buildings.

What are the symptoms?

People who develop Legionnaires’ disease can get seriously ill. Often, hospitalisation is necessary. Symptoms include high temperature (fever), shortness of breath, chest pains, chills, headaches, a persistent cough, vomiting and diarrhoea. It may take a long time before you’re fully recovered.

How do you prevent getting Legionella?

There is no vaccine against Legionella bacteria. At home, you can take measures, such as adjusting the temperature of your water heater (to at least 60 degrees Celsius), draining the garden hose after use, descaling the shower on a regular basis and making sure that your hot tub or Jacuzzi is clean. Quitting smoking reduces the risk of Legionella infection. If you’re travelling abroad, be aware of the increased risk posed by showers, garden hoses and hot tubs that have not been used for a while. Taps and showers that have not been used for a while should be run for a few minutes with hot water, to flush the pipes and kill any bacteria.