LEGIONELLA - World Health Organization

Box . Cold-water tap as a source of fatal nosocom al Legionella pneumon a
n a rehab l tat on centre n the Netherlands
Hoebe et al. (1999) reported two fatal cases of legionellosis in a rehabilitation centre in
the south of Limburg, the Netherlands. The water supply was investigated, and Legionella
was cultured from:
• respiratory patients’ specimens
• water samples and smears from all mixing taps used in showers
• samples from hot and cold-water taps from the infected ward and from the other wards.
The L. pneumophila (serotype I) found in the water supply was the same as that cultured
from the sputum of the two male patients who died of legionellosis.
The cold-water pipes ran alongside both the hot-water pipes and the central heating
system, and the circulating cold water sometimes reached 40 °C, which is within the
growth range of Legionella. Also, the infected ward was closed during weekends,
meaning that the water remained stagnant.
The study’s authors concluded that multiplication of Legionella in the water supply was
probably stimulated by the combination of an elevated cold-water temperature and the
regular stagnation of water.
In northern Europe, about 50% of cases of legionellosis are associated with travel, and the
infection is often associated with hotel water systems (Joseph et al., 1998). Legionella has also
been isolated from water installations in domestic premises; for example, in a study of sporadic
cases of legionellosis in the United Kingdom, legionellae were isolated from approximately
15% of the homes of infected patients but from only about 5% of homes tested as controls
(Coward et al., 1999).
4.2 Water safety plan overview
A WSP needs to be comprehensive; however, an overview of such a plan is shown in Table 4.1,
as an example of the type of information a plan might contain. As explained in Chapter 3, a
WSP is part of a framework for safe water quality that also includes health-based targets and
surveillance.
In the case of the sample WSP shown in Table 4.1, a health-based target for drinking water might
be “Where possible, Legionella should be non-detectable”. Table 4.2 gives examples of healthbased
targets for Legionella. 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.
LEGIONELLA AND THE PREVENTION OF LEGIONELLOSIS