Abstract

Diarrheal diseases remain the second leading cause of death among children under five
globally, responsible for approximately 500,000 deaths annually despite being largely
preventable through water, sanitation, and hygiene (WASH) interventions. This
comprehensive review synthesizes evidence from 140 studies (2000–2025) examining the
impact of WASH interventions on diarrheal disease burden across low- and middle-income
countries (LMICs). We analyze three core intervention categories: water quality
improvements (household water treatment, piped water, chlorine dispensing), sanitation
infrastructure (latrine construction, sewerage, fecal sludge management), and hygiene
promotion (handwashing with soap, behavior change communication). Findings indicate that
handwashing with soap reduces diarrhea risk by 30–48%; household water treatment reduces
risk by 25–50%; and improved sanitation reduces risk by 28–36%. Combined interventions
yield additive effects, with reductions of 30–60% in high burden settings. However, intervention effectiveness varies substantially by context (baseline coverage, infrastructure
quality, behavior change sustainability) and is rarely sustained without continued investment. Large-scale trials (e.g., WASH Benefits, SHINE) showed smaller effects than earlier efficacy
trials, highlighting the gap between controlled studies and real-world implementation. We
recommend integrated WASH delivery, sustained behavior change programming, government
stewardship of rural sanitation, climate-resilient WASH infrastructure, and targeted
interventions for vulnerable populations (displaced persons, urban slums). WASH remains the
most cost-effective diarrheal disease intervention ($3–15 per DALY averted).