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      Interventions to improve water quality for preventing diarrhoea

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          Abstract

          Background

          Diarrhoea is a major cause of death and disease, especially among young children in low-income countries. In these settings, many infectious agents associated with diarrhoea are spread through water contaminated with faeces.

          In remote and low-income settings, source-based water quality improvement includes providing protected groundwater (springs, wells, and bore holes), or harvested rainwater as an alternative to surface sources (rivers and lakes). Point-of-use water quality improvement interventions include boiling, chlorination, flocculation, filtration, or solar disinfection, mainly conducted at home.

          Objectives

          To assess the effectiveness of interventions to improve water quality for preventing diarrhoea.

          Search methods

          We searched the Cochrane Infectious Diseases Group Specialized Register (11 November 2014), CENTRAL (the Cochrane Library, 7 November 2014), MEDLINE (1966 to 10 November 2014), EMBASE (1974 to 10 November 2014), and LILACS (1982 to 7 November 2014). We also handsearched relevant conference proceedings, contacted researchers and organizations working in the field, and checked references from identified studies through 11 November 2014.

          Selection criteria

          Randomized controlled trials (RCTs), quasi-RCTs, and controlled before-and-after studies (CBA) comparing interventions aimed at improving the microbiological quality of drinking water with no intervention in children and adults.

          Data collection and analysis

          Two review authors independently assessed trial quality and extracted data. We used meta-analyses to estimate pooled measures of effect, where appropriate, and investigated potential sources of heterogeneity using subgroup analyses. We assessed the quality of evidence using the GRADE approach.

          Main results

          Forty-five cluster-RCTs, two quasi-RCTs, and eight CBA studies, including over 84,000 participants, met the inclusion criteria. Most included studies were conducted in low- or middle-income countries (LMICs) (50 studies) with unimproved water sources (30 studies) and unimproved or unclear sanitation (34 studies). The primary outcome in most studies was self-reported diarrhoea, which is at high risk of bias due to the lack of blinding in over 80% of the included studies.

          Source-based water quality improvements

          There is currently insufficient evidence to know if source-based improvements such as protected wells, communal tap stands, or chlorination/filtration of community sources consistently reduce diarrhoea (one cluster-RCT, five CBA studies, very low quality evidence). We found no studies evaluating reliable piped-in water supplies delivered to households.

          Point-of-use water quality interventions

          On average, distributing water disinfection products for use at the household level may reduce diarrhoea by around one quarter (Home chlorination products: RR 0.77, 95% CI 0.65 to 0.91; 14 trials, 30,746 participants, low quality evidence; flocculation and disinfection sachets: RR 0.69, 95% CI 0.58 to 0.82, four trials, 11,788 participants, moderate quality evidence). However, there was substantial heterogeneity in the size of the effect estimates between individual studies.

          Point-of-use filtration systems probably reduce diarrhoea by around a half (RR 0.48, 95% CI 0.38 to 0.59, 18 trials, 15,582 participants, moderate quality evidence). Important reductions in diarrhoea episodes were shown with ceramic filters, biosand systems and LifeStraw® filters; (Ceramic: RR 0.39, 95% CI 0.28 to 0.53; eight trials, 5763 participants, moderate quality evidence; Biosand: RR 0.47, 95% CI 0.39 to 0.57; four trials, 5504 participants, moderate quality evidence; LifeStraw®: RR 0.69, 95% CI 0.51 to 0.93; three trials, 3259 participants, low quality evidence). Plumbed in filters have only been evaluated in high-income settings (RR 0.81, 95% CI 0.71 to 0.94, three trials, 1056 participants, fixed effects model).

          In low-income settings, solar water disinfection (SODIS) by distribution of plastic bottles with instructions to leave filled bottles in direct sunlight for at least six hours before drinking probably reduces diarrhoea by around a third (RR 0.62, 95% CI 0.42 to 0.94; four trials, 3460 participants, moderate quality evidence).

          In subgroup analyses, larger effects were seen in trials with higher adherence, and trials that provided a safe storage container. In most cases, the reduction in diarrhoea shown in the studies was evident in settings with improved and unimproved water sources and sanitation.

          Authors' conclusions

          Interventions that address the microbial contamination of water at the point-of-use may be important interim measures to improve drinking water quality until homes can be reached with safe, reliable, piped-in water connections. The average estimates of effect for each individual point-of-use intervention generally show important effects. Comparisons between these estimates do not provide evidence of superiority of one intervention over another, as such comparisons are confounded by the study setting, design, and population.

          Further studies assessing the effects of household connections and chlorination at the point of delivery will help improve our knowledge base. As evidence suggests effectiveness improves with adherence, studies assessing programmatic approaches to optimising coverage and long-term utilization of these interventions among vulnerable populations could also help strategies to improve health outcomes.

          PLAIN LANGUAGE SUMMARY
          Interventions to improve water quality and prevent diarrhoea

          This Cochrane Review summarizes trials evaluating different interventions to improve water quality and prevent diarrhoea. After searching for relevant trials up to 11 November 2014, we included 55 studies enrolling over 84,000 participants. Most included studies were conducted in low- or middle-income countries (LMICs) (50 studies), with unimproved water sources (30 studies), and unimproved or unclear sanitation (34 studies).

          What causes diarrhoea and what water quality interventions might prevent diarrhoea?

          Diarrhoea is a major cause of death and disease, especially among young children in low-income countries where the most common causes are faecally contaminated water and food, or poor hygiene practices.

          In remote and low-income settings, source-based water quality improvement may include providing protected groundwater (springs, wells, and bore holes) or harvested rainwater as an alternative to surface sources (rivers and lakes). Alternatively water may be treated at the point-of-use in people's homes by boiling, chlorination, flocculation, filtration, or solar disinfection. These point-of-use interventions have the potential to overcome both contaminated sources and recontamination of safe water in the home.

          What the research says

          There is currently insufficient evidence to know if source-based improvements in water supplies, such as protected wells and communal tap stands or treatment of communal supplies, consistently reduce diarrhoea in low-income settings ( very low quality evidence). We found no trials evaluating reliable piped-in water supplies to people's homes.

          On average, distributing disinfection products for use in the home may reduce diarrhoea by around one quarter in the case of chlorine products ( low quality evidence), and around a third in the case of flocculation and disinfection sachets ( moderate quality evidence).

          Water filtration at home probably reduces diarrhoea by around a half ( moderate quality evidence), and effects were consistently seen with ceramic filters ( moderate quality evidence), biosand systems ( moderate quality evidence) and LifeStraw® filters ( low quality evidence). Plumbed-in filtration has only been evaluated in high-income settings ( low quality evidence).

          In low-income settings, distributing plastic bottles with instructions to leave filled bottles in direct sunlight for at least six hours before drinking probably reduces diarrhoea by around a third ( moderate quality evidence).

          Research assessing the effects of household connections and chlorination at the point of delivery will help improve our knowledge base. Evidence indicates the more people use the various interventions for improving water quality, the larger the effects, so research into practical approaches to increase coverage and help assure long term use of them in poor groups will help improve impact.

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          Most cited references208

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          Global Causes of Diarrheal Disease Mortality in Children <5 Years of Age: A Systematic Review

          Estimation of pathogen-specific causes of child diarrhea deaths is needed to guide vaccine development and other prevention strategies. We did a systematic review of articles published between 1990 and 2011 reporting at least one of 13 pathogens in children <5 years of age hospitalized with diarrhea. We included 2011 rotavirus data from the Rotavirus Surveillance Network coordinated by WHO. We excluded studies conducted during diarrhea outbreaks that did not discriminate between inpatient and outpatient cases, reporting nosocomial infections, those conducted in special populations, not done with adequate methods, and rotavirus studies in countries where the rotavirus vaccine was used. Age-adjusted median proportions for each pathogen were calculated and applied to 712 000 deaths due to diarrhea in children under 5 years for 2011, assuming that those observed among children hospitalized for diarrhea represent those causing child diarrhea deaths. 163 articles and WHO studies done in 31 countries were selected representing 286 inpatient studies. Studies seeking only one pathogen found higher proportions for some pathogens than studies seeking multiple pathogens (e.g. 39% rotavirus in 180 single-pathogen studies vs. 20% in 24 studies with 5–13 pathogens, p<0·0001). The percentage of episodes for which no pathogen could be identified was estimated to be 34%; the total of all age-adjusted percentages for pathogens and no-pathogen cases was 138%. Adjusting all proportions, including unknowns, to add to 100%, we estimated that rotavirus caused 197 000 [Uncertainty range (UR) 110 000–295 000], enteropathogenic E. coli 79 000 (UR 31 000–146 000), calicivirus 71 000 (UR 39 000–113 000), and enterotoxigenic E. coli 42 000 (UR 20 000–76 000) deaths. Rotavirus, calicivirus, enteropathogenic and enterotoxigenic E. coli cause more than half of all diarrheal deaths in children <5 years in the world.
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            Water, sanitation and hygiene for the prevention of diarrhoea

            Background Ever since John Snow’s intervention on the Broad St pump, the effect of water quality, hygiene and sanitation in preventing diarrhoea deaths has always been debated. The evidence identified in previous reviews is of variable quality, and mostly relates to morbidity rather than mortality. Methods We drew on three systematic reviews, two of them for the Cochrane Collaboration, focussed on the effect of handwashing with soap on diarrhoea, of water quality improvement and of excreta disposal, respectively. The estimated effect on diarrhoea mortality was determined by applying the rules adopted for this supplement, where appropriate. Results The striking effect of handwashing with soap is consistent across various study designs and pathogens, though it depends on access to water. The effect of water treatment appears similarly large, but is not found in few blinded studies, suggesting that it may be partly due to the placebo effect. There is very little rigorous evidence for the health benefit of sanitation; four intervention studies were eventually identified, though they were all quasi-randomized, had morbidity as the outcome, and were in Chinese. Conclusion We propose diarrhoea risk reductions of 48, 17 and 36%, associated respectively, with handwashing with soap, improved water quality and excreta disposal as the estimates of effect for the LiST model. Most of the evidence is of poor quality. More trials are needed, but the evidence is nonetheless strong enough to support the provision of water supply, sanitation and hygiene for all.
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              Diarrhea incidence in low- and middle-income countries in 1990 and 2010: a systematic review

              Background Diarrhea is recognized as a leading cause of morbidity and mortality among children under 5 years of age in low- and middle-income countries yet updated estimates of diarrhea incidence by age for these countries are greatly needed. We conducted a systematic literature review to identify cohort studies that sought to quantify diarrhea incidence among any age group of children 0-59 mo of age. Methods We used the Expectation-Maximization algorithm as a part of a two-stage regression model to handle diverse age data and overall incidence rate variation by study to generate country specific incidence rates for low- and middle-income countries for 1990 and 2010. We then calculated regional incidence rates and uncertainty ranges using the bootstrap method, and estimated the total number of episodes for children 0-59 mo of age in 1990 and 2010. Results We estimate that incidence has declined from 3.4 episodes/child year in 1990 to 2.9 episodes/child year in 2010. As was the case previously, incidence rates are highest among infants 6-11 mo of age; 4.5 episodes/child year in 2010. Among these 139 countries there were nearly 1.9 billion episodes of childhood diarrhea in 1990 and nearly 1.7 billion episodes in 2010. Conclusions Although our results indicate that diarrhea incidence rates may be declining slightly, the total burden on the health of each child due to multiple episodes per year is tremendous and additional funds are needed to improve both prevention and treatment practices in low- and middle-income countries.
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                Author and article information

                Journal
                Cochrane Database Syst Rev
                Cochrane Database Syst Rev
                cd
                The Cochrane Database of Systematic Reviews
                John Wiley & Sons, Ltd (Chichester, UK )
                1469-493X
                20 October 2015
                : 10
                : 1-201
                Affiliations
                [1 ]Department of Environmental Health, Rollins School of Public Health, Emory University Atlanta, USA
                [2 ]Department of Clinical Sciences, Liverpool School of Tropical Medicine Liverpool, UK
                [3 ]Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine London, UK
                [4 ]Aquaya Institute Nairobi, Kenya
                [5 ]Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University Atlanta, USA
                [6 ]Department of Disease Control, Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine London, UK
                Author notes
                Contact address: Thomas F Clasen, Department of Environmental Health, Rollins School of Public Health, Emory University, 1518 Clifton Road NE, Atlanta, GA, 30322, USA. thomas.clasen@ 123456lshtm.ac.uk .

                Editorial group: Cochrane Infectious Diseases Group.

                Publication status and date: Edited (no change to conclusions), published in Issue 10, 2015.

                Review content assessed as up-to-date: 11 November 2014.

                Article
                10.1002/14651858.CD004794.pub3
                4625648
                26488938
                2af7dc83-2da5-4892-97d4-42807e8f89d8
                Copyright © 2015 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
                History
                Categories
                Intervention Review

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