LEGIONELLA - World Health Organization

• validation of the effectiveness of control measures
• verification of the effectiveness of decontamination.
If requirements for testing are included in regulations, it is important to define the purpose
of testing and how results will be treated.
10.3 Scope of regulations
Regulations for control of Legionella should be framed within a preventive risk management
approach that is consistent with the approach outlined in WSPs and the Framework for Safe
Drinking-water (WHO, 2004). Preventive risk management is based on the premise that it is
far better to prevent hazardous situations occurring than to wait until they occur and then
take remedial action.
For operational monitoring, risk management relies on measuring parameters that show whether
systems are working properly, rather than relying on end-point testing, which often only
shows whether a system worked at some earlier time.
Risk management strategies for Legionella should incorporate a multiple barrier approach aimed
at controlling the growth, survival and dissemination of the bacteria. Multiple barriers have
long been used to deal with waterborne organisms. Although all barriers should preferably
remain functional at all times, one advantage of the approach is that if one preventive measure
fails, others may maintain adequate protection.
Specific matters that should be covered by regulations include:
• managerial responsibilities and reporting requirements
• system assessment of buildings and devices that are potential sources of Legionella (e.g. cooling
towers, water distribution systems, spa pools, humidifiers, ice machines); this assessment
should consider the susceptibility of those who may be exposed (e.g. transplant and cancer
patients) and those who are immunocompromised or receiving immunosuppressive treatment
• control measures to prevent the growth, survival and dissemination of Legionella
• operational monitoring procedures to ensure that control measures remain functional
whenever devices are in use
• verification procedures to ensure that WSPs are operating effectively
• mechanisms for surveillance and audit of risk management plans.
Regulations could also include requirements relating to notification of disease and responses
to outbreaks of disease.
LEGIONELLA AND THE PREVENTION OF LEGIONELLOSIS