Upgrading a Piped Water Supply from Intermittent to Continuous Delivery and Association with Waterborne Illness: A Matched Cohort Study in Urban India

BackgroundIntermittent 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 FindingsWe 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 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 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 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.ConclusionsContinuous water supply had no significant overall association with diarrheal disease or ponderal growth in children 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.

研究背景 管道间歇性供水可通过多种途径引发介水疾病（waterborne illness）：管道内壁污染、家庭储水与用水过程中的污染、间歇性供水阶段使用不安全水源，以及卫生用水可及性不足。本研究在印度哈贝利-达瓦德（Hubli-Dharwad）地区，评估了持续供水与间歇性供水模式分别与介水疾病、儿童死亡率以及儿童年龄别体重的关联。

研究方法与结果 我们在该地区开展了一项匹配队列研究（matched cohort study），通过多变量匹配（multivariate matching）筛选出特征可比的间歇性供水与持续供水区域。我们对16个社区的3922户有儿童的家庭进行了随访。整体而言，持续供水与儿童腹泻（患病率比（prevalence ratio，PR）=0.93，95%置信区间（confidence interval，CI）：0.83~1.04，p=0.19）、血性腹泻（PR=0.78，95%CI：0.60~1.01，p=0.06）以及年龄别体重Z评分（weight-for-age z-scores，Δz=0.01，95%CI：-0.07~0.09，p=0.79）无显著关联；与低收入间歇性供水家庭相比，交互检验p值为0.03。在高收入家庭中，持续供水与间歇性供水模式下儿童腹泻病的发生无显著差异。与间歇性供水区域相比，持续供水区域中至少报告1例伤寒病例的家庭数量减少42%（累积发病率比（cumulative incidence ratio，CIR）=0.58，95%CI：0.41~0.78，p=0.001）。持续供水区域与儿童肝炎、霍乱或死亡率无显著关联（p=0.10）。本研究的主要局限性在于：观察性研究设计可能存在未测量混杂因素（confounding），且非盲法干预导致的健康症状报告差异可能引入测量偏倚（measurement bias）。但研究组间阴性对照结局（negative control outcomes）的患病率无显著差异，这表明未检测到混杂因素或测量偏倚。

研究结论 尽管该城市人群存在伤寒沙门菌（Salmonella typhi）及痢疾致病原污染，且实施了集中水处理（centralized water treatment），但整体而言，持续供水与儿童腹泻病或体重增长（年龄别体重相关）无显著关联。持续供水与疾病传播减少相关，尤其在贫困高风险人群亚组中更为显著。