Upgrading a Piped Water Supply from Intermittent to Continuous Delivery and Association with Waterborne Illness

A Matched Cohort Study in Urban India

Citation: Ercumen A, Arnold BF, Kumpel E, Burt Z, Ray I, Nelson K, et al. (2015) Upgrading a Piped Water Supply from Intermittent to Continuous Delivery and Association with Waterborne Illness: A Matched Cohort Study in Urban India. PLoS Med 12(10): e1001892. doi:10.1371/journal.pmed.1001892
Published: October 27, 2015

Background: Intermittent delivery of piped water can lead to waterborne illness through contamination in the pipelines or during household storage, use of unsafe water sources during intermittencies, and limited water availability for hygiene. We assessed the association between continuous versus intermittent water supply and waterborne diseases, child mortality, and weight for age in Hubli-Dharwad, India.
Methods and Findings: We conducted a matched cohort study with multivariate matching to identify intermittent and continuous supply areas with comparable characteristics in Hubli-Dharwad. We followed 3,922 households in 16 neighborhoods with children <5 y old, with four longitudinal visits over 15 mo (Nov 2010–Feb 2012) to record caregiver-reported health outcomes (diarrhea, highly credible gastrointestinal illness, bloody diarrhea, typhoid fever, cholera, hepatitis, and deaths of children <2 y old) and, at the final visit, to measure weight for age for children <5 y old. We also collected caregiver-reported data on negative control outcomes (cough/cold and scrapes/bruises) to assess potential bias from residual confounding or differential measurement error.
Continuous supply had no significant overall association with diarrhea (prevalence ratio [PR] = 0.93, 95% confidence interval [CI]: 0.83–1.04, p = 0.19), bloody diarrhea (PR = 0.78, 95% CI: 0.60–1.01, p = 0.06), or weight-for-age z-scores (Δz = 0.01, 95% CI: −0.07–0.09, p = 0.79) in children <5 y old. In prespecified subgroup analyses by socioeconomic status, children <5 y old in lower-income continuous supply households had 37% lower prevalence of bloody diarrhea (PR = 0.63, 95% CI: 0.46–0.87, p-value for interaction = 0.03) than lower-income intermittent supply households; in higher-income households, there was no significant association between continuous versus intermittent supply and child diarrheal illnesses. Continuous supply areas also had 42% fewer households with ≥1 reported case of typhoid fever (cumulative incidence ratio [CIR] = 0.58, 95% CI: 0.41–0.78, p = 0.001) than intermittent supply areas. There was no significant association with hepatitis, cholera, or mortality of children <2 y old; however, our results were indicative of lower mortality of children <2 y old (CIR = 0.51, 95% CI: 0.22–1.07, p = 0.10) in continuous supply areas. The major limitations of our study were the potential for unmeasured confounding given the observational design and measurement bias from differential reporting of health symptoms given the nonblinded treatment. However, there was no significant difference in the prevalence of the negative control outcomes between study groups that would suggest undetected confounding or measurement bias.
Conclusions: Continuous water supply had no significant overall association with diarrheal disease or ponderal growth in children <5 y old in Hubli-Dharwad; this might be due to point-of-use water contamination from continuing household storage and exposure to diarrheagenic pathogens through nonwaterborne routes. Continuous supply was associated with lower prevalence of dysentery in children in low-income households and lower typhoid fever incidence, suggesting that intermittently operated piped water systems are a significant transmission mechanism for Salmonella typhi and dysentery-causing pathogens in this urban population, despite centralized water treatment. Continuous supply was associated with reduced transmission, especially in the poorer higher-risk segments of the population.

Editors' Summary
Groundwater_Contamination_Latin_America_SmBackground: Access to a safe drinking water supply (a water source that is protected from contamination with microbes or chemicals) and to adequate sanitation facilities (improved latrines and other facilities that prevent people from coming into contact with human feces) is essential for good health. Unimproved water supplies and sanitation, together with poor hygiene, increase the transmission of waterborne diseases, many of which cause diarrhea (passing three or more loose or liquid stools a day). Notably, diarrheal diseases such as cholera and dysentery kill more than three-quarters of a million children under 5 y old every year. In 2000, therefore, world leaders set a target of reducing the proportion of the global population without access to safe drinking water and basic sanitation to half of the 1990 level by 2015 as part of Millennium Development Goal 7 (MDG7; this MDG and seven others aim to eradicate extreme poverty globally). Worldwide, according to the 2015 MDG report, 2.6 billion people have gained access to improved drinking water since 1990 (91% of the world’s population now has access to an improved drinking water supply compared to 76% in 1990), and 2.1 billion people have gained access to improved sanitation.
Why Was This Study Done? The MDG target for access to safe drinking water was met by 2010, but more than 600 million people still lack access to an improved water source. Even more people lack access to piped water, the highest category of improved supply (other improved supplies include boreholes and protected wells). Moreover, piped water is only supplied intermittently in many cities in low-income countries, which can lead to waterborne illnesses through contamination in pipelines or during household storage between supply cycles and through the use of alternative unsafe water supplies. In this matched cohort study, the researchers investigate the association between continuous versus intermittent piped water supplies and waterborne diseases, mortality (death), and weight for age (an indicator of overall health and growth) among young children in Hubli-Dharwad, an Indian conurbation where about 10% of the population has a continuous piped water supply but the rest of the population only receives piped water intermittently. A matched cohort study compares outcomes in groups of people exposed to different (nonrandomized) interventions who are matched for other characteristics that might affect the outcome to allow an unbiased comparison.
What Did the Researchers Do and Find? The researchers matched the eight areas of Hubli-Dharwad with a continuous water supply to eight comparable areas with an intermittent water supply. Key characteristics used to identify matched areas included socioeconomic status and sanitation conditions. The researchers made four visits to 3,922 households in these areas with at least one child under 5 y old over a 15-mo study period to record caregiver-reported illness among young children, child deaths, and, at the final visit, the children’s weight for age. Compared to an intermittent water supply, there was no overall association between a continuous water supply and diarrhea, bloody diarrhea (dysentery), or weight-for-age scores among children aged <5 y, death before the age of 2 y, or hepatitis and cholera in the study population. However, there was a lower occurrence of bloody diarrhea among children aged <5 y in lower-income households that had a continuous water supply than in lower-income households that had an intermittent supply, and continuous supply areas had fewer household cases of typhoid fever than intermittent supply areas.
What Do These Findings Mean? The study’s reliance on caregiver reports of illnesses among young children and potential unmeasured differences between areas with intermittent versus continuous supply may affect the accuracy of these findings. Nevertheless, the study data suggest that these sources of bias are unlikely. These findings suggest that, compared to having an intermittent water supply, having a continuous water supply was not associated with diarrheal disease or growth (judged by weight) among children aged <5 y in Hubli-Dharwad. That is, having a continuous piped water supply was not associated with a reduction in waterborne diseases overall among young children in this setting. This finding could reflect contamination of water during continued water storage in households with a continuous supply (it takes time to change old habits) and/or exposure to organisms (pathogens) that cause diarrhea through nonwaterborne routes. Importantly, however, the finding that a continuous supply was associated with a reduction in typhoid fever and more severe forms of waterborne illness among children in lower-income households suggests that intermittently operated water systems can serve as a transmission route for waterborne pathogens in urban populations despite centralized treatment of water to make it safe to drink.
Additional Information: This list of resources contains links that can be accessed when viewing the PDF on a device or via the online version of the article at http://dx.doi.org/10.1371/journal.pmed.1001892.

  • This study is further discussed in a PLOS Medicine Perspective by Clarissa Brocklehurst and Tom Slaymaker
  • A PLOS Medicine Collection on water and sanitation is available
  • The World Health Organization (WHO) provides information on water, sanitation and health (in several languages), including information on waterborne diseases and on drinking water quality; it also provides detailed information on diarrhea
  • The WHO/United Nations Children's Fund (UNICEF) Joint Monitoring Programme for Water Supply and Sanitation (JMP) is the official United Nations mechanism tasked with monitoring progress toward MDG7, Target 7B; the JMP Update Report 2015 is available online (key facts are available in several languages through the JMP website)
  • The children’s charity UNICEF, which protects the rights of children and young people around the world, provides information on water, sanitation and health and on diarrhea (in several languages)
  • The nongovernmental organization Practical Action provides information and approaches and technologies for improving urban water supplies


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