Legionellosis is an environmental-source disease caused by Legionella bacteria. Many such diseases are prevented using a scientifically-based risk management process called Hazard Analysis and Critical Control Point (HACCP; pronounced “Hassip”). Water Management Plans based on HACCP have been proven effective for preventing legionellosis. Perspective is given for how published guidance and standards can impact the practice of AWT members. Just released for public comment on 01 October 2010, ASHRAE Standard 188P - Prevention of Legionellosis Associated with Building Water Systems makes use of the HACCP process.
Failure to prevent legionellosis is the most significant water treatment problem today. Essentially every case of disease is the result of exposure to inadequately managed building water systems.
The number of legionellosis outbreaks in the US has now surpassed the number of waterborne outbreaks of gastrointestinal disease (CDC 2008 Presentation at American Water Works Association 2008 annual meeting in Atlanta, GA to be published in MMWR on Sept. 18, 2008; http://www.awwa.org/publications/MainStreamArticle.cfm?itemnumber=36670)
Officially reported cases have risen substantially in the US; between 2002 and 2003 reported cases increased 70% followed by a sustained increase since then. Legionellosis is most commonly reported for persons aged 45-64 years with 63% of cases in people younger than 65 and incidence rates in the US show strong seasonality with most cases reported in summer or fall (Neil 2008). This seasonality has been substantiated by studies in other regions of the world(Karagiannis 2008).
Legionellosis is the condition of being infected with Legionella bacteria. Disease symptoms range from mild flu-like effects through to severe pneumonia resulting in serious systemic effects. Public awareness of the disease and interest in the legal community has increased in the US due to increasingly large lawsuit settlements and jury trials.
Legionellosis is an environmental-source disease because the causative agents, Legionella bacteria, are found commonly in natural aquatic environments (rivers, lakes, soils). Typically, in the natural environment, Legionella are found in very low numbers. Amplification in hot or tepid water systems can result in exposure to massive numbers of Legionella bacteria if the building water is aerosolized or aspirated. Transmission is limited to inhalation of contaminated water; person-to-person transmission of disease has never been documented.
The Occupational Safety and Health Administration (OSHA) have categorized the presence of Legionella bacteria in building water systems as potentially hazardous. Under federal law via the the General Duty Clause in the OSH Act, employers are required to 'furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees'. The General Duty Clause covers failures to follow recognized good industry practices for instances in which Legionnaires' disease has been linked to poorly maintained water systems (OSHA 2005; http://www.osha.gov/SLTC/legionnairesdisease/standards.html ).
Complete eradication of Legionella bacteria is not possible because they are so widely distributed in the environment. But it is possible to prevent thousands of cases of legionellosis just as it is also accomplished for many other environmental-source diseases. By far, the most widely used and effective environmental-disease prevention process is the hazard analysis and critical control point system.