A water-borne outbreak of norovirus and multiple diarrheagenic Escherichia coli infections during Eid-Karasu, Turkey, August 2018

  • Water or foodborne
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Background:
On August 24, 2018, City Health Directorate reported more than a 10-fold increase in patients with diarrhea in emergency room of Karasu public hospital (the only health center available during Eid in this district). We investigated the cause of the outbreak and implemented control measures.

Methods:
A suspected case was a Karasu district resident diagnosed with gastroenteritis-related ICD-10 codes (R11, K52) among outpatients during 20-27 August. A probable case was a suspected case with diarrhea and vomiting. We conducted a case-control investigation, among 175 randomly selected probable cases and their neighbor controls through face-to-face interview. Exposure was characterized by hygiene habits, consumption of tap, fountain and bottled water. We compared exposures of probable cases with neighbor controls (175:175) to calculate odds ratios (ORs) and 95% confidence intervals (CIs). We collected six clinical specimens and 19 water samples. Pathogens were identified using culture Methods: and PCR.

Results:
Attack rate of suspected cases, widespread in the district, was 2.9% (1815/62866). The number of cases peaked on 22 August and the epidemic curve revealed a point-source outbreak. Of probable cases, 74.3% (130/175) drank tap water, compared with 62.3% (109/175) of controls (OR=1.8, 95%CI=1.1-2.8). Shiga-toxin producing Escherichia coli, enteropathogenic E. coli, and enteroaggregative E. coli and norovirus were isolated from human specimens. Thirteen water samples (including the one from the main water tank supplying the whole district) tested positive (>1CFU/100ml) for total Coliform (1-920 CFU/100ml) and/or Escherichia coli (1-720 CFU/100ml). Free chlorine levels were below 0.2 ppm in seven samples. Main water storage tank and pipes were in bad condition.

Conclusion:
Epidemiological and environmental investigations pointed towards contamination of water distribution system with fecal pathogens. Upon decision in a multi-stakeholder meeting, water tank was hyperclorinated and chlorination devices were implemented, renewal of water distribution system was decided. We conducted health education on hygiene practices and safe water consumption. Number of cases decreased following the interventions.

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