Page 40 - GPHS Environmental Public Health Standards (Foundation of Public Health) v1

Potable Water - Main risks - Harmful microbes in water

Legionella

➢ Legionella bacteria are the cause of legionellosis, including

Legionnaires’ disease.
➢ The bacteria are abundant in the environment and can grow at

temperatures found in piped distribution systems.
➢ The route of infection is by inhalation of droplets or aerosols; however,
exposure from piped water systems is preventable through the

implementation of basic water quality management measures.
➢ This includes maintaining water temperature outside the range at which

Legionella proliferates (25–50°C) and maintaining disinfectant
residuals throughout the piped distribution system.
➢ Whenever water temperatures are found in the critical range of 25–50

°C, Legionella testing should be performed to assess the health risk for
consumers.