Since the initial outbreak in 1976 that led to the discovery and identification of Legionnaires’ disease, much has been discovered about the bacteria (Legionella) that causes the disease and the disease itself. This includes how Legionnaires’ disease is contracted and how to minimize risk of disease contraction, as well as effective medical treatments for Legionnaires’ disease. However, guidelines for “100%” disease prevention and control remain at large, as well as any uniform consensus on the routine testing (monitoring) for Legionella in the water systems that may harbor the bacteria. Existing guidelines and statements, however, do provide substantial direction and information that can be adopted to effectively control and minimize legionellosis.

This document is a comprehensive update of collective information and data available from numerous research, investigative, and authoritative sources on Legionella and legionellosis. These include the CDC (Centers for Disease Control and Prevention), OSHA (Occupational Safety and Health Administration), WHO (World Health Organization), EPA (Environmental Protection Agency), various state public health agencies, as well as associated technical trade organizations and recognized Legionella experts and commercial entities. Due to the multi-disciplined, technical and medical nature of the subject, this document is directed at summarizing and presenting Legionella in an up-to-date, informative, and useful format to the water treatment professional and end-user, as well as for the general public. Extensive references are cited that may provide more detailed and in-depth information on legionellosis and related topics to benefit those with more specific interest and application or decision making needs.