Tick-host-virus triad in Crimean-Congo hemorrhagic fever transmission: global patterns across vector and reservoir species.

Crimean-Congo hemorrhagic fever virus (CCHFV) is a widely distributed tick-borne orthonairovirus and an important public health threat across Africa, Asia, Europe, and the Middle East. This narrative review synthesizes evidence on the tick-host-virus transmission system, with emphasis on Hyalomma vectors, vertebrate hosts, viral genomic diversity, vector competence, occupational exposure, molecular diagnostics, and One Health surveillance. Published systematic reviews and meta-analyses are used as secondary evidence sources; no de novo pooled meta-analysis was performed in this review. CCHFV comprises a tripartite RNA genome with substantial segment-specific diversity and frequent reassortment, complicating lineage assignment and molecular epidemiology. Hyalomma ticks are the principal recognized vectors, while domestic livestock can develop transient, generally asymptomatic viremia that supports tick-host-tick transmission. Human risk is concentrated in occupational and healthcare settings involving ticks, livestock, infected tissues, or infected patients. The geographic distribution of Hyalomma ticks is changing in parts of Europe and may expand northward under suitable environmental conditions, although detection of adventitious ticks should be distinguished from evidence of established populations. Effective prevention requires integrated vector control, personal protection, livestock and tick surveillance, genomic monitoring, rapid diagnostics, and coordinated One Health response. Important evidence gaps remain in non-Hyalomma vector competence, standardized animal serosurveillance, genomic sampling, climate-driven establishment of Hyalomma populations, and validation of point-of-care diagnostics across viral lineages.