Abstract:

Inadequate water, sanitation and hygiene (WASH) are major contributors to the global burden of infectious diseases in low and middle income countries. Poor or unsafe WASH conditions drive high rates of diarrhoeal diseases, soil-transmitted helminth infections, trachoma, and other communicable illnesses, disproportionately affecting children under five and contributing significantly to disability adjusted life years (DALYs). This narrative review synthesizes evidence on the effectiveness of WASH interventions in reducing infectious disease incidence and morbidity. We examine point-of-use water quality interventions, managed water systems, improved sanitation facilities, hygiene promotion, and integrated WASH packages. Evidence indicates that handwashing with soap consistently reduces diarrhoeal and respiratory infections, while improved sanitation and water supply interventions yield variable results depending on coverage, adherence, and environmental factors. Cluster randomized trials, including WASH Benefits and SHINE, highlight the limited impact of household level interventions without broader community coverage. Disease specific outcomes, such as cholera, typhoid, schistosomiasis, and healthcare associated infections, demonstrate that multi-component WASH strategies can interrupt transmission pathways, including faecal oral and hygiene mediated routes. Implementation challenges, including behaviour change, infrastructure reliability, governance, and equity considerations, are critical determinants of intervention success. Economic analyses underscore the cost-effectiveness of WASH programs, particularly when integrated with broader public health initiatives. This review identifies research gaps in long-term impact evaluation, pathogen specific outcomes, and equity focused assessments. Sustained investment in WASH infrastructure, community level intervention saturation, and evidence informed policy frameworks are essential to maximize the preventive potential of WASH against infectious diseases.