Public health officials will normally take action at accommodation sites following an association with a cluster of cases of Legionnaires' disease. This paper seeks to determine the likelihood of such a cluster occurring at a site once it has been associated with a single case of the disease, and therefore whether more should be done at sites following individual cases.
Information for UK residents reported to the EWGLINET system between 1993 and 2000 was included in a dataset. The size and country of hotel visited by the cases were divided into six country groups (France, Italy, Spain, Turkey, other Europe and other World), and eight size groups (<20 rooms, 20-49, 50-99, 100-199, 200-299, 300-399, 400-499, 500+). The data were investigated using Cox proportional hazards regression to model the probability of at least one further case following the first.
The dataset comprised 793 cases that had stayed at 605 sites in 51 countries between 1993 and the end of 2000. This included 605 cases that were the first case associated with a site, and 188 subsequent cases. Following the first case, 16.6% of sites were associated with at least one subsequent case during the period under study. The probability of a subsequent case occurring within 6 months of the first varied by country and size group, with some combinations returning a probability >30%; the probability of a subsequent case occurring within 2 years of the first reached over 50% in some instances.
There may be support for early intervention at some accommodation sites following a first case of Legionnaires' disease, in specific country and size groups.