A Bayesian shared-component spatiotemporal model applied to Global Burden of Disease 2023 data across 204 countries reveals that STI co-occurrence burden is sharply geographically concentrated. Eswatini (score 2.25), Lesotho (2.13), Malawi (1.90), Mozambique (1.89), and South Africa (1.85) ranked highest, with 57 countries showing high directional stability (posterior exceedance probability >0.95), predominantly in sub-Saharan Africa and the Caribbean. The shared spatial score correlated negatively with the Socio-demographic Index (ρ = −0.619) and predicted HIV/AIDS mortality with an incidence rate ratio of 14.64 per standard deviation — a striking magnitude.
The analytic architecture here is methodologically ambitious: decomposing country-level STI incidence into shared versus disease-specific spatial and temporal components allows researchers to isolate true geographic co-vulnerability from disease-specific noise. That the rankings proved near-perfectly stable across prior sensitivity analyses (ρ ≥ 0.9999) strengthens confidence in the hierarchy. Practically, this scoring framework could sharpen resource allocation for integrated STI screening programs — a priority WHO has explicitly flagged. However, the model operates at country level, masking subnational heterogeneity that likely drives local transmission dynamics. GBD input data quality also varies substantially across low-income settings, potentially compressing true burden estimates in the most affected regions. Secondary and anogenital herpes, syphilis, gonorrhea, and chlamydia likely contribute differentially to the shared signal but are not individually parsed here. As a preprint not yet peer-reviewed, these findings warrant independent validation before informing policy directly — but the spatial scoring tool itself represents a genuinely useful epidemiological advance.