Clostridium difficile infection, hospital geography and time-space clustering.

To analyse spatial and temporal relationships of Clostridium difficile-associated disease in an inner-city hospital, we retrospectively evaluated 283 episodes of confirmed C. difficile diarrhoea in the Chelsea and Westminster Hospital between 1995 and 1998, against a background of relatively stable case mix, antibiotic usage and admission numbers, using Knox analysis to determine the presence of disease clustering in time and space. We found five time-space clusters on four medical wards and between two adjacent units. The clusters were not related to the overall case number on single wards, and were separated in time. Knox time-space analysis provides a simple screening tool to identify disease clusters, assess the efficacy of infection control measures and the influence of hospital geography and traffic. The results support the importance of infection control measures in the prevention of C. difficile-related disease.