LEGIONELLA - World Health Organization

6.3 System assessment
This section should be read in conjunction with Section 3.3.1 of Chapter 3. The steps involved
in system assessment, some of which are discussed further below, are to:
• assemble a team to prepare the WSP
• document and describe the system (Section 6.3.1)
• assess hazards and prioritize risks (Section 6.3.2)
• assess the system.
6.3.1 Document and describe the system
A system assessment for health-care facilities should consider the well-described infection
reservoirs in community-acquired Legionnaires’ disease; for example, potable and in-building
water systems (discussed in Chapter 4) and cooling towers and evaporative condensers (discussed
in Chapter 5); in addition, the assessment should assess the type of health care provided, and
the immune and health status of the individuals using the facilities. Table 6.2 details the types
of system components that should be considered.
Table . Examples of system components to be cons dered n system assessment
and subsequent hazard analys s n health-care fac l t es
System component Comment Reference
Hot and cold-water systems Evidenced and epidemiologically
based associations
See Chapter 4
Cooling towers and
evaporative condensers
See Chapter 5
Respiratory devices
(including nebulizers and
ventilatory machines)
Levy & Rubin (1998)
Medical humidifiers filled
and rinsed with tap water
Levy & Rubin (1998)
Birthing pool water Levy & Rubin (1998)
Drinking water dispensers Any epidemiological links are unclear. Rechenburg,
(not discussed further in An investigation of drinking water Engelhart
this chapter)
dispensers in hospitals found
Legionella in 4 out of 50 dispensers.
An association with Legionella
infections was not investigated.
& Exner (2001)
Water systems in dental These have sometimes been shown Pankhurst et al.
units (not discussed to be heavily colonized with Legionella, (1990, 2003)
further in this chapter) particularly where there are multiple
chairs (e.g. in dental schools), but no
cases of Legionnaires’ disease have
been attributed to dental units.
Dentists have been found to have
high titres of Legionella antibodies.
LEGIONELLA AND THE PREVENTION OF LEGIONELLOSIS