LEGIONELLA - World Health Organization

Table . Water safety plan overv ew
Process step Water source D str but on
Assess hazards
and pr or t ze r sks
(example)
↓
Ident fy control
measures
(example)
↓
Mon tor control
measures
(example)
↓
Prepare
management
procedures
(example)
Establ sh
ver f cat on and
surve llance
(example)
Develop support ng
programmes
(example)
High nutrients
and microbial load
in source water
Routine disinfection
of water at 0.3–
0.5 mg/l free residual
chlorine (depending
on the national
regulations)
Chlorine on line with
chlorine/redox probe
Turbidity on line
Point-of-use filtration
and disinfection
programme; possible
treatment for
dissolved solids
Stagnant water
in deadlegs in the
pipework, resulting
in proliferation of
legionellae
Routine cleaning
procedures for
distribution system,
and review of system
flow diagram
Chloramination a
Routine review of
process flow diagram
(desktop and onsite)
to identify areas of
concern or stagnation
Removal of deadlegs
where possible
Resp ratory
apparatus
Legionellae entering
respiratory apparatus
in tap water, being
inhaled by patient and
leading to potential
Legionnaires’ disease
Use of sterilized or
point-of-use filtered
water to clean
respiratory equipment
Cleaning and disinfection
protocol for
respiratory apparatus;
microbiological monitoring
programme
Monitoring of water
sterilization devices
Monitoring of cleaning
protocol records
Isolation of unit and
disinfection of source
• Internal audit and external audit (by the health department) to
confirm that operational monitoring and corrective actions are
being undertaken as stated in the WSP
• Monthly heterotrophic colony counts at the tap and in the source
water (to track trends and changes, rather than as an absolute
indicator, and to be undertaken by an accredited laboratory)
• Three-monthly sampling for legionellae of water in the distribution
system and at the point of use
• Respiratory apparatus must be disinfected on a regular daily basis
and between every patient; also, it must be regulated in the
hospital hygiene plan
• Staff training and education; maintenance and calibration
a Not currently available for individual buildings. In Europe the levels permitted are lower than in USA which may
affect the results.
LEGIONELLA AND THE PREVENTION OF LEGIONELLOSIS