District-level HIV and TB health system vulnerability to climate and weather hazards in South Africa: a composite index approach

Background Climate change and extreme weather events (EWEs) threaten health systems, disrupt continuity of HIV and TB services, amplify communicable disease burdens, and exacerbate health inequities in South Africa. Yet few empirical studies have quantified district-level vulnerability, where HIV and TB service delivery and climate adaptation are operationalised. Methods We developed a district-level composite HIV/TB Vulnerability Index, integrating indicators of HIV & tuberculosis burden (sensitivity), health system capacity, and socio-economic vulnerability. We also developed a Hazard Index which when combined with the HIV/TB vulnerability Index, identifies districts where underlying vulnerability coincides with higher likelihood of EWEs. Indicators were drawn from national surveys, routine health information systems, and international hazard datasets, normalised using a min-max scaling, and aggregated with equal weighting. Sensitivity analysis were conducted to assess the robustness of the composite indices. Findings The most vulnerable districts were located in the Northern Cape, Eastern Cape and KwaZulu Natal provinces where high HIV/TB burden and socio-economic sensitivity coincided with limited health system adaptive capacity. In contrast, the least vulnerable districts, were concentrated in Gauteng and Western Cape, reflecting stronger health system capacity and more favourable socio-economic conditions. Hazard exposure exhibited a clear spatial division with western districts experiencing greater heat stress and eastern districts facing higher flood and heavy-rainfall hazards. When hazard exposure was combined with the HIV/TB vulnerability Index, districts with both high vulnerability and hazard scores clustered predominantly along the east coast (Ugu, uMkhanyakude, and Harry Gwala in KwaZulu-Natal, and O.R. Tambo and Alfred Nzo in the Eastern Cape). Interpretation South Africa's district-level vulnerability to climate and weather hazards is driven by the convergence of high HIV/TB burden, constrained health system capacity, and socio-economic disadvantage. Where this vulnerability intersects with increased hazard risk, it creates a compound susceptibility that needs attention. Our findings provide evidence for geographically targeted adaptation, prioritising continuity of HIV/TB services, health system resilience, and hazard-specific preparedness.