LEGIONELLA - World Health Organization

water treatments (including chemicals and antimicrobials). The water quality in health-care
facilities needs special attention, determined by the susceptibility of the patients; patients
undergoing a severe immunosuppressive therapy (e.g. organ transplant or cancer therapy) are
particularly at risk of infection.
Further information on health-based targets and information on surveillance for Legionella
can be found in Sections 3.2 and 3.4 of Chapter 3, respectively.
The remainder of this chapter provides information relevant to a WSP specific for cooling
towers and evaporative condensers, for each of the three main areas of a WSP:
• system assessment (Section 5.3)
• monitoring (Section 5.4)
• communication and management (Section 5.5).
Sections 5.3–5.5 should be read in conjunction with Section 3.3 from Chapter 3.
Cooling towers and evaporative condensers are often designed simply to optimize heat transfer
and thermal efficiency, and the practices described here might not be included in typical water
treatment programmes for such devices. However, an effective water treatment programme
that reduces the risk of legionellosis and thus ensures safer operation of the system also leads
to more efficient operation (because there is less fouling) and longer system life (because there
is less corrosion) (Broadbent, 1996).
Fundamentally, the responsibility for managing the risk of legionellosis belongs to the facility
owner or manager. To ensure that the risk management plan is properly implemented, the owner
or manager should assign tasks, ensure that documentation is complete and current, and hold
people accountable.
LEGIONELLA AND THE PREVENTION OF LEGIONELLOSIS