Sub-national estimates of incidence of visceral leishmaniasis and optimisation of geographical accessibility to treatment centres in Kenya

Visceral leishmaniasis (VL) remains a major public health challenge, disproportionally affecting populations with limited access to timely diagnosis and treatment. National summaries often mask substantial local heterogeneity in disease risk and healthcare access, limiting their usefulness for targeted control and elimination. We analysed ten years (2016–2025) of routine facility-based surveillance data from Kenya using Bayesian small-area estimation and geospatial accessibility modelling to quantify fine-scale variation in disease burden, identify key determinants, and optimise access to treatment services. A total of 11,985 cases were reported, corresponding to an estimated incidence of 10 cases per 100,000 population per year, with marked seasonality and epidemic periods. Disease burden was highly focal: five northern counties accounted for 86% of all cases, with further clustering at sub-county and ward levels. Predicted VL incidence exceeded 100 cases per 100,000 person-years in several wards, predominantly in Turkana and West Pokot counties. Higher temperatures, poverty, and poor housing quality were positively associated with increased probability of VL occurrence and higher case counts, whereas higher precipitation was negatively associated. Under the current configuration of 46 treatment centres, only 45% of the population in need could access care within 120 minutes of motorised travel. Adding five optimally located facilities increased this 120-minute coverage to 76%, with diminishing gains from further expansion. Together, these findings demonstrate how integrating small-area disease modelling with geospatial accessibility analysis can reveal hidden inequities in VL burden and inform more equitable and efficient deployment of treatment services, supporting targeted interventions and accelerating progress towards elimination.