Guidelines for investigating single cases of Legionnaires' disease.

These guidelines for the investigation of single cases of legionnaires' disease have been updated from those produced in 1994 to take account of developments in microbiological and environmental diagnostic capabilities and the recognition that infection may be acquired from the patient's domestic water system. The new guidelines recommend that when a case of legionnaires' disease has been diagnosed, it should be investigated to determine whether it is part of an outbreak or cluster, work related, suspected to be a hospital acquired infection or is travel associated. If information concerning the patient's movements during the incubation period shows it to be none of these, then appropriate environmental investigations should be considered which might include the patient's domestic water system as a potential source of infection. The guidelines are designed to provide advice and information to all public health personnel involved in the control and prevention of legionnaires' disease.