An outbreak of leptospirosis in Orissa, India: The importance of surveillance

Abstract

OBJECTIVE: To demonstrate the importance of surveillance systems in detecting emerging diseases and highlighting the strengths and weaknesses of an existing one. METHODS: The Orissa multi-disease surveillance system (OMDSS) was introduced in November 1999. Reporting units from the periphery send data to the district on a weekly basis. These reports are analysed regularly. A district task force (DTF) was available to intervene in the event of an outbreak. The OMDSS detected an increasing number of cases with fever and jaundice in June 2002. The DTF investigated this outbreak using clinical, epidemiological and laboratory tools to identify its cause. RESULTS: This outbreak, in a remote corner of India, was detected within 4 days by an existing surveillance system. Action was initiated within 24 h, but it took approximately two more weeks for the causative agent to be diagnosed. A total of 143 people were suspected to have leptospirosis between 23 June 2002 and 31 July 2002. The attack rate was 5.95% and the case fatality ratio (CFR) was 7.69%, both lower than outbreaks reported elsewhere in India. While males were infected more often than females, the CFR was higher among females and among the 6-15 year age groups. Exposure to infected water in a canal was the probable cause of the outbreak. IgM antibodies were positive in 33 of the patients and six patients tested positive for PCR and culture. Leptospirosis interrogans serovar canicola, Leptospirosis interrogans serovar pomona and Leptospirosis interrogans serovar hebdomadis were isolated. CONCLUSIONS: Leptospirosis is a new disease in this region of India. This outbreak was detected and diagnosed because of the surveillance system. The prompt response helped in containing the outbreak early enough. However, the morbidity and mortality could have been further mitigated if the delays in transmitting information had been minimized. An adequate laboratory support would have also helped considerably. We conclude stressing the importance of surveillance as a public health tool.