Molecular Evolution and Phylogeography of the Crimean-Congo Hemorrhagic Fever Virus

The Crimean-Congo hemorrhagic fever virus (CCHFV) is a single-stranded, segmented RNA virus belonging to the Nairoviridae family, and it is rapidly expanding across Africa, Asia, and southern Europe, probably favored by climate change and livestock trade. Its fatality rate in humans reaches up to 40%, and there is currently no specific treatment or vaccine available. Therefore, the development of therapies against CCHFV is essential, and their design requires understanding of the molecular evolution and genetic distribution of the virus. Motivated by these concerns, we present a comprehensive review of the molecular evolution, genetic characterization, and phylogeography of CCHFV, and we discuss their potential implications for therapeutic design. Specifically, we describe the virus's capacity to increase its genetic diversity through numerous mutations, recombination events, and genomic reassortments, which affect fundamental viral functions such as RNA binding, host-virus interactions, viral entry, and polymerase activity. We also assess the presence of temporal heterogeneous rates of evolution and molecular adaptation among CCHFV coding regions, where purifying selection is generally predominant but diversifying selection is observed in molecular regions associated with host adaptation and transmission. We emphasize the importance of understanding the complex molecular evolution of CCHFV for the rational design of therapies and highlight the need for efforts in surveillance, evolutionary prediction, and therapeutic development.