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PLoS One. 2012;7(10):e47239. doi: 10.1371/journal.pone.0047239. Epub 2012 Oct 10.

Shigellosis outbreak associated with contaminated well water in a rural elementary school: Sichuan Province, China, June 7-16, 2009.

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  • 1Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, People's Republic of China.



We investigated a shigellosis outbreak in an elementary school to identify the source of infection, mode of transmission and risk factors for illness.


In a case-control investigation, we compared the source of drinking water, consumption of untreated well water and suspected food items, and hygienic habits between case-students and randomly selected asymptomatic control-students, frequency-matched by class on a 1:1 ratio.


18% of the 533 students and no teachers developed Shigella. 52%(44/85) of case-students and 17% (12/71) of control-students drank untreated well water (OR = 2.3, 95% CI = 1.1-5.8); 47% (n = 40/85) of case-students and 14% (10/71) of control-students drank untreated water from Well A (OR = 3.7, 95% CI = 1.3-11). The odds ratio increased with the amount of untreated Well A water consumed (p = 0.035, χ(2) test for trend). Rectal swabs from 5 of 6 case-students and water from Well A yielded Shigella flexneri 2b.


This shigellosis outbreak was caused by drinking untreated water from a well polluted by Shigella flexneri 2b.

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