Legionnaires' disease on a cruise ship linked to the water supply system: Clinical and public health implications

The occurrence of legionnaires' disease has been described previously in pa ssengers of cruise ships, but determination of the source has been rare. A 67-year-old, male cigarette smoker with heart disease contracted legionnair es' disease during a cruise in September 1995 and died 9 days after disemba rking. Legionella pneumophila serogroup 1 was isolated from the patient's s putum and the ship's water supply. Samples from the air-conditioning system were negative. L, pneumophila serogroup 1 isolates from the water supply m atched the patient's isolate, by both monoclonal antibody subtyping and gen omic fingerprinting, None of 116 crew members had significant antibody tite rs to L. pneumophila serogroup 1. One clinically suspected case of legionna ires' disease and one confirmed case were subsequently diagnosed among pass engers cruising on the same ship in November 1995 and October 1996, respect ively. This is the first documented evidence of the involvement of a water supply system in the transmission of legionella infection on ships. These c ases were identified because of the presence of a unique international syst em of surveillance and collaboration between public health authorities.