Cooling-water systems have
been the source of outbreaks of Legionnaires disease, and the causative organism
Legionella pneumophila has been identified in 44% of such systems. Re-circulating cooling
water systems require regular maintenance and treatment.
Recommendations to reduce the risk of outbreaks of the disease arising from this
source have been issued by the Department of Health and Social Security (DHSS). Chlorine
has been reported as ineffective, especially in the presence of organic matter or at pH 8
or higher. (Department of Virology, John Radcliffe Hospital, Oxford, U.K.)