High-quality shared sanitation is protective against excreta-related health outcomes: Evidence from India, Kenya, and Uganda.

Shared sanitation is widely used in rapidly growing informal settlements globally, but is classified as "limited" by current global monitoring standards due to concerns over hygiene, safety, and health risks. While previous studies have identified key features of high-quality shared sanitation, it remains unclear which aspects most strongly influence health outcomes. This study aimed to: (1) identify shared sanitation quality factors associated with diarrhea, stomach pain, and urinary tract infection (UTI); (2) construct a composite indicator of high-quality shared sanitation; and (3) assess whether associations vary across countries. We conducted a cross-sectional study of 5700 households using shared sanitation in informal settlements in Delhi (India), Nairobi (Kenya), and Kampala (Uganda) between June 2025 and January 2026. We assessed five sanitation quality domains - sharing intensity, cleanliness, hygiene, privacy/safety, and accessibility - and examined associations with health outcomes using multilevel logistic regression models. Overall, 14.5% of households reported diarrhea, 13.0% stomach pain, and 10.3% UTI. Sharing intensity was modestly associated with diarrhea (aOR: 1.04 per additional household [95% CI: 1.02-1.07]), while visible fecal contamination in the facility was strongly associated with all outcomes. In composite analyses, facilities meeting ≥4 quality criteria among 6 primary indicators (no visible feces/urine; water available for flushing/cleaning; functional handwashing station; lighting availability; lockable from inside; 24-h access) were consistently protective against diarrhea (aOR: 0.50 [0.41-0.62]), stomach pain (aOR: 0.45 [0.35-0.58]), and UTI (aOR: 0.36 [0.29-0.46]). These findings suggest that incremental improvements in shared sanitation quality may reduce health risks, and moving toward quality-based metrics may better inform investment priorities.