Introduction to Legionella

Legionella is a common bacterium found in natural environments including ponds, rivers, and lakes. The bacteria can also be supplied in small counts within mains water supply. Where there is water and the conditions of creating water droplets (aerosol), people using or within the area of these services may be at risk.

Legionnaires Disease is a form of pneumonia, which can be fatal. The most at risk are the very old and the very young, the ill and smokers to name a few. Legionella bacteria can also cause other, less harmful illness such as Pontiac fever and Lochgoilhead fever, which can affect all people.

The main route of infection is through inhalation, by inhaling airborne water droplets that contain Legionella. It cannot be spread from person to person. The majority of cases or outbreaks of the disease have been via domestic water services, evaporative cooling towers, and spa pools.

There are a number of factors that are required to create risk of legionellosis. These contributing factors include:

• the presence of legionella
• the presence of population vulnerable to exposure
• a means of creating aerosol
• suitable conditions for Legionella to proliferate
• lack of control & management measures

The conditions and contributing factors to legionella growth include:

• temperatures between 20-45°C
• available nutrients (including sediment, biofilm, algae, scale, rust, material, etc.)
• presence of biofilm on surfaces of water
• poor or in adequate management including training and awareness