LEGIONELLA - World Health Organization

Nutrients — control measures
Bathers have a responsibility to ensure hygienic practices, and should be encouraged to:
• shower before immersion, preferably using soap (adequate signs should be visible, explaining
the need)
• adhere to limits set for the number of bathers allowed at any one time
• limit the time spent in the pool.
Ideally, the jet pumps of hot tubs should cut out automatically after 15–20 minutes, so that
bathers are encouraged to leave the water and the disinfectant levels allowed to recover (see
also Disinfection below).
Spa pools should have clearly visible information listing the range of pre-existing medical
conditions for which bathing in such pools is not recommended.
Because of the high bather-to-water ratio in hot tubs, it is important to ensure that the water
turnover is adequate. Guideline figures vary from six minutes in the United Kingdom (Health
Protection Agency, 2006) 8 to one hour in New South Wales, Australia (New South Wales
Health, 1996). 9
Disinfection — control measures
Choice of disinfectant
The microbial and chemical quality of the water used for filling pools and hot tubs will affect
the efficacy of disinfection. Ideally, a detectable residual biocide level should be maintained
at all times, to prevent colonization of the system by microorganisms living in biofilms.
Biocides used in hot tubs and pools are commonly oxidizing biocides; for example, chlorine
or bromine, sometimes combined with additional treatment regimes such as ultraviolet (UV)
light or ozone. Because UV and ozone have no systemic residual effect, they should be used
with a residual biocide to improve control and reduce by-products. Alternatively, nonoxidizing
biocides, such as polyhexamethylene biguanide and copper/silver ionization (usually
with an oxidizing biocide) may be used. Particular features of hot tubs (such as elevated
temperatures, high turbulence, high organic load, the amount of sunlight present and natural
water chemistry) may affect the choice of disinfectant.
Halogen-based oxidizing disinfectants, such as chlorine, are most commonly used in pools and
hot tubs. They have the advantage of being relatively inexpensive, simple to use, easy to
measure on site, and active against most infectious organisms. Many commercial and chemical
8 www.hpa.org.uk/publications/ 2006/spa_pools/spa_pools_part1.pdf (accessed 29 March 2006)
9 http://www.health.nsw.gov.au/public-health/ehb/general/pools/publicpools.html (accessed 12 July 2005)
LEGIONELLA AND THE PREVENTION OF LEGIONELLOSIS