Factors associated with diarrhoeal morbidity in HIV-exposed infants: a cross-sectional analysis of WaSH-HIV intersections in Kasungu, Malawi

Background Poor water, sanitation, and hygiene (WaSH) conditions may undermine clinical interventions for HIV-exposed infants (HEI) in low-resource settings. Although cotrimoxazole prophylaxis reduces bacterial diarrhoea, its effectiveness is limited where environmental pathogen loads remain high. This study examined how household WaSH characteristics influence two-week diarrhoeal prevalence among HEI in Malawi. Methods A systematic sample of 291 HEI was drawn from 899 eligible participants in Kasungu District. Data collection integrated caregiver interviews, clinical record audits, and household inspections using WHO/UNICEF Joint Monitoring Programme metrics. Two-week diarrhoea was defined as ≥ 3 loose stools within 24 h. Multivariable logistic regression generated adjusted odds ratios (AORs) controlling for sociodemographic, environmental, and biomedical factors. Results Severe WaSH deficits were widespread: 79.7% of households had no hygiene service, 73.5% had poor-quality latrines, and 84.5% lacked handwashing compliance. Basic drinking-water service showed the strongest association with diarrhoea (AOR 14.38; 95% CI 6.51–31.75), followed by limited service (AOR 8.78; 95% CI 4.58–16.83). Poor neonatal nevirapine adherence increased risk (AOR 6.87; 95% CI 1.30–36.24). Conclusion Household WaSH conditions were strongly associated with caregiver-reported diarrhoeal morbidity among HEI, with effect sizes exceeding those of biomedical or sociodemographic factors. Within this cross-sectional design, clinical prophylaxis should be interpreted alongside the environmental conditions in which HEI live. Programme discussions may consider whether improved water access, sanitation quality, and hygiene infrastructure could be relevant contextual components of HIV-related child-health services, while recognising that causal inference is not possible.