title: Cholera outbreak linked with lack of safe water supply following a tropical cyclone in Pondicherry, India, 2012.
abstract: In the aftermath of a severe cyclonic storm on 7 January 2012, a cluster of acute diarrhoea cases was reported from two localities in Pondicherry, Southern India. We investigated the outbreak to identify causes and recommend control measures. We defined a case as occurrence of diarrhoea of more than three loose stools per day with or without vomiting in a resident of affected areas during 6-18 January 2012. We used active (door-to-door survey) and stimulated passive (healthy facility-based) surveillance to identify cases. We described the outbreak by time, place, and person. We compared the case-patients with up to three controls without any apparent signs and symptoms of diarrhoea and matched for age, gender, and neighbourhood. We calculated matched odds ratio (MOR), 95% confidence intervals (CI), and population attributable fractions (PAF). We collected rectal swabs and water samples for laboratory diagnosis and tested water samples for microbiological quality. We identified 921 cases and one death among 8,367 residents (attack rate: 11%, case-fatality: 0.1%). The attack rate was the highest among persons of 50 years and above (14%) and females (12%). The outbreak started on 6 January and peaked on the 9th and lasted till 14 January. Cases were clustered around two major leakages in water supply system. Nine of the 16 stool samples yielded V. cholerae O1 Ogawa. We identified that consumption of water from the public distribution system (MOR=37, 95% CI 4.9-285, PAF: 97%), drinking unboiled water (MOR=35, 95% CI 4.5-269, PAF: 97%), and a common latrine used by two or more households (MOR=2.7, 95% CI 1.3-5.6) were independently associated with cholera. Epidemiological evidence suggested that this outbreak was due to ingestion of water contaminated by drainage following rains during cyclone. We recommended repair of the water supply lines, cleaning-up of the drains, handwashing, and drinking of boiled water.
authors.affiliation: ICMR School of Public Health, National Institute of Epidemiology, Indian Council of Medical Research, TNHB, Ayapakkam, Chennai 600 077, India.
authors.forename: Tony
authors.initials: T
authors.lastname: Fredrick
authors.affiliation: ICMR School of Public Health, National Institute of Epidemiology, Indian Council of Medical Research, TNHB, Ayapakkam, Chennai 600 077, India.
authors.forename: Manickam
authors.initials: M
authors.lastname: Ponnaiah
authors.affiliation: ICMR School of Public Health, National Institute of Epidemiology, Indian Council of Medical Research, TNHB, Ayapakkam, Chennai 600 077, India.
authors.forename: Manoj V
authors.initials: MV
authors.lastname: Murhekar
authors.affiliation: ICMR School of Public Health, National Institute of Epidemiology, Indian Council of Medical Research, TNHB, Ayapakkam, Chennai 600 077, India.
authors.forename: Yuvaraj
authors.initials: Y
authors.lastname: Jayaraman
authors.affiliation: ICMR School of Public Health, National Institute of Epidemiology, Indian Council of Medical Research, TNHB, Ayapakkam, Chennai 600 077, India.
authors.forename: Joseph K
authors.initials: JK
authors.lastname: David
authors.affiliation: ICMR School of Public Health, National Institute of Epidemiology, Indian Council of Medical Research, TNHB, Ayapakkam, Chennai 600 077, India.
authors.forename: Selvaraj
authors.initials: S
authors.lastname: Vadivoo
authors.affiliation: ICMR School of Public Health, National Institute of Epidemiology, Indian Council of Medical Research, TNHB, Ayapakkam, Chennai 600 077, India.
authors.forename: Vasna
authors.initials: V
authors.lastname: Joshua
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D002771:Cholera / Q000175:diagnosis / Q000453:epidemiology*; D055867:Cyclonic Storms; D003967:Diarrhea / Q000453:epidemiology / Q000382:microbiology; D004196:Disease Outbreaks; D005260:Female; D006801:Humans; D007194:India / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D014871:Water Microbiology; D014881:Water Supply; D055815:Young Adult
keywords: Cholera; India; Outbreak; Post-cyclone