Evaluation of ultraviolet light for disinfection of hospital water contaminated with Legionella.

An epidemic of nosocomial Legionella micdadei pneumonia occurred among renal transplant patients in the University of Virginia hospital between 1978 and 1982. Although no further cases were diagnosed after 1982, filters and ultraviolet light (UVL) fittings were installed in 1985 as an attempt to disinfect water piped to rooms of transplant patients, because of concern about persistence of L micdadei in hospital water. Water samples were obtained from eight UVL-treated rooms and eight control rooms. 26 of 95 control samples were culture positive for L micdadei compared with 0 of 71 samples of filtered, UVL-treated water (p less than 0.0001, Fisher's exact test). After the UVL fitting and filter had been bypassed because of a leak, 9 of 33 samples from the UVL rooms were positive (p less than 0.0001). These data suggest that UVL treatment may be useful in continuous disinfection of water in the hospital rooms of high-risk patients.