LEGIONELLA - World Health Organization

A risk assessment for cooling towers and evaporative condensers in health-care facilities should
take into account the proximity of cooling tower exhausts to the air inlets for wards housing
high-risk patients, such as those who have undergone renal transplants.
Respiratory apparatus and tubing — risk factors
In addition to the normal inhalation risks, patients in health-care facilities are at greater risk
when forced to inhale water in respiratory devices that may contain legionellae (Marrie et al.,
1991; Blatt, Parkinson & Pace, 1993; Yu, 1993; Venezia et al., 1994; Kool et al., 1998). For
example, inhalation of contaminated aerosols may occur when tap water is used to rinse or
fill respiratory devices, tubing for use in mechanical ventilation machines and chambers of
hand-held medication nebulizers. Nosocomial aspiration pneumonia has been reported in
patients, particularly after surgery where there is intubation (Blatt, Parkinson & Pace, 1993;
Yu, 1993; Venzia et al., 1994). Patients with Legionnaires’ disease were found to have undergone
tracheal tube placement significantly more often or to have been intubated for significantly
longer than patients with other types of pneumonia (Yu, 2000).
A retrospective review of microbial and serological data from the laboratories of a hospital in
the United States of America (USA) dealt with clusters of cases of Legionnaires’ disease among
hospitalized patients (Kool et al., 1998). By reviewing the charts of patients over a period of
10 years, the authors identified 25 culture-confirmed cases of nosocomial or possibly nosocomial
Legionnaires’ disease, in which 12 patients (48%) died. For cases that occurred before 1996,
intubation was associated with increased risk of disease. High-dose corticosteroid medication
was strongly associated with a risk for disease. Six or seven available clinical isolates were
identical and were indistinguishable by pulse-field gel electrophoresis from environmental
isolates from the water system.
Birthing pool water — risk factors
The important role of pool water — especially of hot tubs — as infection reservoirs of Legionella
is well established (see Chapter 8). The first report of a newborn contracting L. pneumophila
pneumonia after water birth was in 2001 (Franzin et al., 2001). Because the hospital water
supply and, particularly, the pool water for water birthing were contaminated by L. pneumophila
serogroup 1, the newborn was infected — perhaps by aspiration — after a prolonged delivery
in the contaminated water.
6.4 Monitoring
This section should be read in conjunction with Section 3.3.2 of Chapter 3. The steps
involved in monitoring, some of which are discussed below, are to:
• identify control measures (Section 6.4.1)
• monitor control measures (Section 6.4.2)
• validate effectiveness of the WSP.
LEGIONELLA AND THE PREVENTION OF LEGIONELLOSIS