title: Chlorination of Household Drinking Water Among Cholera Patients' Households to Prevent Transmission of Toxigenic Vibrio cholerae in Dhaka, Bangladesh: CHoBI7 Trial.
abstract: Household members of cholera patients are at a 100 times higher risk of cholera infections than the general population because of shared contaminated drinking water sources and secondary transmission through poor household hygiene practices. In this study, we investigated the bactericidal concentration of free chlorine required to inactivate Vibrio cholerae in household drinking water in Dhaka, Bangladesh. In laboratory experiments, we found that the concentrations of free chlorine required to inactivate 105colony-forming units (CFU)/mL of V. cholerae serogroups O1 and O139 were 0.1 mg/L and 0.2 mg/L, respectively. The concentration of free chlorine generated by a single chlorine tablet (sodium dichloroisocyanurate [33 mg]) after a 30-minute reaction time in a 10-L sealed vessel containing Dhaka city municipal supply water was 1.8 mg/L; and the concentration declined to 0.26 mg/L after 24 hours. In field measurements, water collected from 165 households enrolled in a randomized controlled trial (RCT) of a chlorine and handwashing with soap intervention (Cholera-Hospital-Based-Intervention-for-7-Days [CHoBI7]), we observed significantly higher free chlorine concentrations in the 82 intervention arm households (mean = 1.12 mg/L, standard deviation [SD] = 0.52, range = 0.07-2.6 mg/L) compared with the 83 control households (0.017 mg/L, SD = 0.01, range = 0-0.06 mg/L) (P < 0.001) during spot check visits. These findings suggest that point-of-use chlorine tablets present an effective approach to inactivate V. cholerae from drinking water in households of cholera patients in Dhaka city. This result is consistent with the findings from the RCT of CHoBI7 which found that this intervention led to a significant reduction in symptomatic cholera infections among household members of cholera patients and no stored drinking water samples with detectable V. cholerae.
authors.affiliation: International Centre for Diarrheal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh.
authors.forename: Mahamud-Ur
authors.initials: MU
authors.lastname: Rashid
authors.affiliation: Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland.
authors.forename: Christine Marie
authors.initials: CM
authors.lastname: George
authors.affiliation: International Centre for Diarrheal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh.
authors.forename: Shirajum
authors.initials: S
authors.lastname: Monira
authors.affiliation: International Centre for Diarrheal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh.
authors.forename: Toslim
authors.initials: T
authors.lastname: Mahmud
authors.affiliation: International Centre for Diarrheal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh.
authors.forename: Zillur
authors.initials: Z
authors.lastname: Rahman
authors.affiliation: International Centre for Diarrheal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh.
authors.forename: Munshi
authors.initials: M
authors.lastname: Mustafiz
authors.affiliation: International Centre for Diarrheal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh.
authors.forename: K M
authors.initials: KM
authors.lastname: Saif-Ur-Rahman
authors.affiliation: International Centre for Diarrheal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh.
authors.forename: Tahmina
authors.initials: T
authors.lastname: Parvin
authors.affiliation: International Centre for Diarrheal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh.
authors.forename: Sazzadul Islam
authors.initials: SI
authors.lastname: Bhuyian
authors.affiliation: International Centre for Diarrheal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh.
authors.forename: Fatema
authors.initials: F
authors.lastname: Zohura
authors.affiliation: International Centre for Diarrheal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh.
authors.forename: Farzana
authors.initials: F
authors.lastname: Begum
authors.affiliation: International Centre for Diarrheal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh.
authors.forename: Shwapon Kumar
authors.initials: SK
authors.lastname: Biswas
authors.affiliation: International Centre for Diarrheal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh.
authors.forename: Shamima
authors.initials: S
authors.lastname: Akhter
authors.affiliation: Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland.
authors.forename: Xiaotong
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland.
authors.forename: David
authors.initials: D
authors.lastname: Sack
authors.affiliation: Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland.
authors.forename: R Bradley
authors.initials: RB
authors.lastname: Sack
authors.affiliation: International Centre for Diarrheal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh. munirul@icddrb.org.
authors.forename: Munirul
authors.initials: M
authors.lastname: Alam
mesh_terms: D001459:Bangladesh; D002713:Chlorine / Q000737:chemistry; D002771:Cholera / Q000517:prevention & control* / Q000635:transmission; D060766:Drinking Water / Q000737:chemistry*; D005191:Family Characteristics; D054879:Halogenation; D006801:Humans; D014734:Vibrio cholerae; D018508:Water Purification / Q000379:methods; D014881:Water Supply / Q000592:standards
chemical_list: D060766:Drinking Water; D002713:Chlorine