ABSTRACT
The emergence of an outbreak of leptospirosis in a nurses' hostel in Chennai presented a challenge to identify and control the source of the outbreak. Sixty-nine residents and staff members were interviewed to assess exposure factors. Blood samples from the acute and convalescent patients were tested with the Microscopic Agglutination Test using the serovars prevalent in Chennai. Polymerase Chain Reaction (PCR) was conducted on serum and water samples. Based on preliminary investigation, control measures with standard hygienic measures were instituted. The attack rate was 35%. The epidemic curve suggested continuous or intermittent exposure to infection over a five-week period. Twenty residents (three asymptomatic) developed laboratory confirmed Leptospira icterohemorrhagiae. Residents collected water from an underground storage tank that was filled twice weekly from a mobile water tanker with a bucket on a rope, and the tank was usually left open. PCR tests confirmed the presence of leptospires from this water. Other control measures included cleaning the large backyard with its many stray dogs and rats, chlorinating water supplies, boiling drinking water and health education. No further cases occurred twelve days after implementing control measures. Access to clean water, not only for drinking but also for bathing, brushing and washing is essential to prevent water-borne outbreaks.