LEGIONELLA - World Health Organization

Agency, Legionella Section, United Kingdom, personal communication, October 2005).
Procedures for control and prevention of hotel-associated legionellosis have been published
elsewhere (Crespi, 1993; Anon, 1999; HSE, 2004). The European guidelines give detailed
definitions and procedures for responding to travel-associated cases (EWGLI, 2002, 2003). 7
Ship-associated Legionnaires’ disease is preventable. The principles for control of land-based
water systems and for WSPs applied to piped water supplies in the engineered building
environment (see Chapter 4) are applicable to the control of systems on ships.
Source water quality — control measures
International health regulations require ports to supply potable water to ships; however, there
is no requirement for potable water to be Legionella-free, and such a requirement would be
unrealistic. The water taken on board should be of potable quality and from a reliable source.
Since the reliability of the water supply cannot always be guaranteed, precautions should be
taken to ensure that the water is adequately disinfected on board.
Hot and cold-water systems — control measures
Primary and secondary methods of prevention and control, as applied to hotels, are based on
experience acquired in managing outbreaks and are largely empirical. These measures do not,
in general, differ from those that are applied to other types of buildings, in that they aim to
eradicate Legionella in the installations by means of a risk assessment that focuses on:
• factors leading to Legionella proliferation (e.g. the long periods of stagnation that occur in
water systems in hotels and hotel rooms)
• implementation of remedial measures (e.g. removal of dead and blind ends, maintenance
of elevated temperatures in the hot-water system, periodic disinfection and permanent
chlorination of the cold-water system).
The efficacy of these measures in the control and secondary prevention of outbreaks is well
established, although they may be insufficient in hotels repeatedly associated with cases. An
example of a checklist specifically designed for water systems in hotels is provided in Appendix 1.
In ships, onboard exposure through piped water can be prevented by such water quality management
measures as:
• treating source water (where the water is non-potable)
• maintaining water temperatures outside the range in which Legionella proliferates (25–50 ºC)
• maintaining disinfection residuals greater than 0.2 mg/litre throughout the piped distribution
system and storage tanks (WHO, 2004).
7 http://www.ewgli.org/public_info/publicinfo_european_guidelines.asp
LEGIONELLA AND THE PREVENTION OF LEGIONELLOSIS