Ecological Analysis of Under-Five Diarrhoea Morbidity and Water, Sanitation, and Hygiene Coverage in Zamfara State, North West Nigeria

Diarrhoeal morbidity in children under five is inextricably linked to deficiencies in water, sanitation, and hygiene (WASH) infrastructure. In Zamfara State, one of Nigeria's most WASH-deprived states, the spatial relationship between WASH coverage and childhood diarrhoea burden has not been rigorously quantified. This ecological study analyses the district-level association between WASH coverage indicators and under-five diarrhoea morbidity rates across the 14 local government areas of Zamfara State using data from the 2021 Nigeria Multiple Indicator Cluster Survey (MICS), state WASH baseline reports, and routine Health Management Information System (HMIS) morbidity data for 2021 to 2023. WASH coverage indicators included access to improved water sources, open defaecation rates, and handwashing with soap prevalence. Spearman correlation and negative binomial regression were employed for ecological association analysis. Districts with open defaecation rates above 60% had a 2.8-fold higher diarrhoea morbidity rate per 1,000 children under five compared to districts below 30%. Access to improved water was inversely correlated with diarrhoea morbidity (rho negative 0.61, p less than 0.01). Handwashing with soap prevalence showed the strongest inverse association with diarrhoea incidence (rho negative 0.74). The ecological associations held after controlling for healthcare facility density. These findings provide district-level evidence to prioritise WASH investment in the highest-burden LGAs of Zamfara State as a child health strategy. Keywords: diarrhoea, WASH, ecological analysis, Zamfara State, North West Nigeria.