Health & Safety Risk Management System

H05 - Legionella

Legionnaires’ disease acquired its name in 1976 when an outbreak of pneumonia occurred among people attending a convention of the American Legion in Philadelphia. Scientists identified the causative agent as a previously unknown bacterium subsequently named Legionella pneumophila. The disease is a potentially fatal form of pneumonia which can affect anybody, but which principally affects those who are susceptible because of age, illness, immunosuppression, smoking, etc.

The responsible bacterium and related bacteria are found naturally in environmental water sources such as rivers, lakes and reservoirs and generally pose no problems. However, purpose-built water systems such as whirlpool spas and cooling towers in which temperatures are warm enough to encourage growth of the bacteria, can cause outbreaks of Legionnaires’ disease. It is important to note that it does not spread from person to person.

Due to a lack of statistics, the frequency of this disease occurring in workplaces cannot be evaluated or estimated, however, knowledge of the bacteria responsible for the disease indicates that there are some workers more at risk than others. Those with occupations that require them to work in sealed buildings including those who maintain cooling towers in air-conditioning systems need to be monitored. Additionally, some outdoor workers should be considered at risk as soil disturbed by bulldozing and areas where surface or aerosolized water discharge occurs can cause exposure to Legionella pneumophila.

To prevent the occurrence of Legionnaires’ disease, employers must comply with regulations requiring them to manage, maintain and treat purpose-built water systems properly. The Legionella Procedure is written to help companies comply with legislation.