Building climate-resilient health systems for the displaced: health information systems and the statistical invisibility of climate-related mobility in sub-Saharan Africa.

Background: Climate change is reshaping the populations health systems serve, yet health information systems (HIS) remain blind to one of the fastest-growing groups: people displaced or migrating in the context of climate change. In sub-Saharan Africa this mobility is now counted at scale, but mobility data and health data systems have developed as parallel infrastructures blind to each other's populations. Objective: To examine the health of populations moving in the context of climate change in sub-Saharan Africa, and to argue that a principal obstacle to climate-resilient health policy is the failure of the health-information-systems building block to render them legible. Methods: Structured, non-exhaustive searches of PubMed, Scopus and Google Scholar (June-July 2026), complemented by institutional data sources (WHO, IOM, IDMC, World Bank) and humanitarian situation reporting, organised into three evidence streams: (i) health outcomes of climate-related movers in sub-Saharan Africa, (ii) health information system performance in the region, and (iii) theoretical scholarship on enumeration and legibility. Eligibility criteria, search strings and the selection process are reported in full. Results: Sub-Saharan African HIS are structurally constrained: only about one in ten deaths in the WHO African Region is recorded, DHIS2-based routine systems capture facility events rather than populations, and household surveys sample by residence. Against this baseline, climate-related mobility is linked to malnutrition, waterborne disease, psychosocial distress and unmet basic needs, with markedly gendered impacts. Yet displacement datasets rarely capture health, health surveys rarely record displacement, a dedicated migration module appeared in only 12 of 85 reviewed DHS surveys, and climate attribution ranges from 3% to 99% across contexts. Health-system responses concentrate in acute emergency delivery, leaving information systems unadapted. Conclusions: Populations invisible to routine health information systems are excluded from anticipatory, climate-resilient health policy. Three low-cost adaptations, health modules in displacement tracking, mobility modules in health surveys, and a harmonised typology of climate-related mobility, would make them visible to health-system planning at marginal cost, and are implementable within platforms (DHIS2, DTM, DHS) already operating at national scale.