title: Legionnaires' disease associated with a hospital water system. A five-year progress report on continuous hyperchlorination.
abstract: In 1981, sixteen cases of nosocomial legionellosis occurred among 456 patients admitted to a new hematology-oncology unit (35 per 1000 admissions). Monoclonal antibody typing and restriction endonuclease plasmid analysis identified a unique strain (09,04) of Legionella pneumophila serogroup 1 isolated from both patients and water outlets. Continuous hyperchlorination of the hot and cold water began in January 1982, and chlorine levels of 3 to 5 mg/L have been maintained most recently. Water samples have been consistently negative for Legionella for more than five years. Four sporadic cases of nosocomial legionellosis have occurred in the hematology-oncology unit during the same period (one per 1000 admissions) associated with a different strain of L pneumophila serogroup 1 (09,00). The environmental reservoir(s) of L pneumophila serogroup 1 in these cases has not been identified. Levels of trihalomethanes (potential carcinogens) were high (greater than 100 micrograms/L) when chlorine levels of hot water exceeded 4 mg/L. Some corrosion damage to the water distribution system has occurred: the average number of leaks per month increased steadily from zero in 1982 to 5.2 in 1986. The chlorinator installation costs were +75,800, and annual operation expenses were +12,500. Continuous hyperchlorination is a promising but still experimental technique for control of nosocomial legionellosis. In our experience, epidemic disease has been controlled, but sporadic cases have continued to occur.
authors.affiliation: Department of Internal Medicine, University of Iowa College of Medicine, Iowa City.
authors.forename: C M
authors.initials: CM
authors.lastname: Helms
authors.forename: R M
authors.initials: RM
authors.lastname: Massanari
authors.forename: R P
authors.initials: RP
authors.lastname: Wenzel
authors.forename: M A
authors.initials: MA
authors.lastname: Pfaller
authors.forename: N P
authors.initials: NP
authors.lastname: Moyer
authors.forename: N
authors.initials: N
authors.lastname: Hall
mesh_terms: D002713:Chlorine; D003428:Cross Infection / Q000453:epidemiology / Q000517:prevention & control*; D006785:Hospitals, University; D006801:Humans; D006846:Hydrocarbons, Halogenated / Q000032:analysis; D007484:Iowa; D007875:Legionella / Q000302:isolation & purification; D007877:Legionnaires' Disease / Q000453:epidemiology / Q000517:prevention & control*; D008697:Methane / Q000031:analogs & derivatives / Q000032:analysis; D013997:Time Factors; D014871:Water Microbiology; D014881:Water Supply / Q000032:analysis
chemical_list: D006846:Hydrocarbons, Halogenated; D002713:Chlorine; D008697:Methane