Hubbard Sydney, Wolf Jennyfer, Oza Hemali H, Arnold Benjamin F, Freeman Matthew C, Levy Karen
Gangarosa Department of Environmental Health, Rollins School of Public Health, Emory University, Atlanta, Georgia, USA.
Department of Environment, Climate Change and Health, World Health Organization, Geneva, Switzerland.
Environ Health Perspect. 2025 Feb;133(2):26001. doi: 10.1289/EHP14502. Epub 2025 Feb 4.
Studies evaluating how water, sanitation, and/or handwashing (WASH) interventions in low- and middle-income countries impact diarrheal diseases have shown inconsistent results. The prevalence of enteric pathogen infections and diarrhea are highly seasonal and climate-sensitive, which could explain heterogeneous findings. Understanding how season influences the effectiveness of WASH interventions is critical for informing intervention approaches that will be resistant under the varying weather conditions that climate change will bring.
We conducted a systematic review of the literature and meta-analysis to test whether and to what extent the impact of WASH interventions on diarrhea differs by season. We searched the literature for randomized and nonrandomized controlled WASH intervention trials and identified the season in which data were collected-rainy, dry, or both-for each study using proximate land station weather datasets. We compared the relative risk (RR) estimates for the impact of interventions on diarrhea for each study, stratified by season, and analyzed estimates using meta-analysis and meta-regression. This study is registered with PROSPERO, CRD42021231137.
A total of 50 studies met the inclusion criteria, resulting in 34 drinking water intervention estimates, 8 sanitation intervention estimates, and 14 handwashing intervention estimates. Of the total studies, 60% () spanned more than one season, with most single-season studies (75%, ) occurring exclusively in the dry season. The effect of WASH interventions was stronger in dry seasons than in rainy seasons, with a 33% [95% confidence interval (CI): 24%, 41%] and 18% reduction (95% CI: 5%, 29%) in diarrhea risk, respectively. When stratified by type of intervention, the stronger effect size in dry seasons was consistent for water and handwashing interventions but not for sanitation interventions.
Estimates of the seasonal impact of WASH interventions revealed larger effects in the dry season than in the rainy season overall and for water and handwashing interventions in particular. These patterns likely affected previous estimates of intervention effectiveness, which included more dry season estimates. These findings suggest the need to collect data across seasons and report seasonally stratified results to allow for more accurate estimates of the burden of disease impacted by WASH investments and to improve projections of potential impacts of these interventions under future climate conditions. These findings also underscore the need for robust WASH interventions designed to be resistant to seasonal variations in temperature and rainfall now and under future climate change scenarios. https://doi.org/10.1289/EHP14502.
评估低收入和中等收入国家的水、环境卫生和/或洗手（WASH）干预措施如何影响腹泻疾病的研究结果并不一致。肠道病原体感染和腹泻的患病率具有高度季节性且对气候敏感，这可能解释了研究结果的异质性。了解季节如何影响WASH干预措施的有效性对于制定在气候变化带来的不同天气条件下仍具抗性的干预方法至关重要。
我们对文献进行了系统综述和荟萃分析，以检验WASH干预措施对腹泻的影响是否以及在多大程度上因季节而异。我们在文献中搜索了随机和非随机对照的WASH干预试验，并使用附近陆地站天气数据集为每项研究确定收集数据的季节——雨季、旱季或两者皆有。我们比较了每项研究中按季节分层的干预措施对腹泻影响的相对风险（RR）估计值，并使用荟萃分析和荟萃回归分析估计值。本研究已在PROSPERO注册，注册号为CRD42021231137。
共有50项研究符合纳入标准，得出34项饮用水干预估计值、8项环境卫生干预估计值和14项洗手干预估计值。在所有研究中，60%（）跨越了不止一个季节，大多数单季节研究（75%，）仅发生在旱季。WASH干预措施在旱季的效果比雨季更强，腹泻风险分别降低了33%[95%置信区间（CI）：24%，41%]和18%（95%CI：5%，29%）。按干预类型分层时，旱季更强的效应量在水和洗手干预中是一致的，但在环境卫生干预中并非如此。
WASH干预措施季节性影响的估计显示，总体上旱季的影响大于雨季，特别是水和洗手干预。这些模式可能影响了先前对干预效果的估计，其中包括更多旱季的估计。这些发现表明需要跨季节收集数据并报告按季节分层的结果，以便更准确地估计WASH投资所影响的疾病负担，并改善对这些干预措施在未来气候条件下潜在影响的预测。这些发现还强调了现在以及在未来气候变化情景下，需要设计出对温度和降雨的季节性变化具有抗性的强有力的WASH干预措施。https://doi.org/10.1289/EHP14502
