14 Facts about Legionella and Legionellosis

Legionella is a rod shaped waterborne bacterium.

Legionella bacteria is found in natural water sources, such as ponds, lakes and rivers. However, the bacteria is not likely harmful or will cause infection. It is also found in man-made systems.

Legionellosis is the collective name given to the pneumonia-like illness and diseases caused by Legionella bacteria.

In order to contract diseases, a person would breathe in fine droplets of water, otherwise known as aerosols, that are infected with the bacteria.

Legionnaires' Disease is the most commonly known disease of Legionellosis and has a fatality of 10% worldwide. The number of cases of the disease in the UK is thought to be underestimated due to lack of diagnosis.

Symptoms of Legionnaires' Disease usually begin to show in 2 - 10 days. Untreated Legionnaires’ disease usually worsens during the first week.

Legionnaires' Disease cannot be passed from person to person.

According to a Norwegian study, Legionella bacteria can spread more than 10km (over 6 miles) in the air.

Of the reported cases of Legionellosis, 75–80% are over 50 years and 60–70% are male worldwide.

Legionnaires’ disease is a notifiable disease, meaning local health authorities must be informed by doctors if a case is diagnosed to help with tracing the source of a potential outbreak.

Many countries have a legal obligation in place to complete water sampling. This is not a legal requirement in the UK.

There are over 50 species of Legionella bacteria. Legionella pneumophila is the species most associated with Legionnaires’ disease in the UK, as it is responsible for 90% of outbreaks.

Legionella thrives at temperatures between 20-45°C and nutrients, such as rust and limescale, increase the rate of proliferation.

At temperatures below 20°C, the bacteria can survive but do not multiply as they are rendered dormant.