Crimean-Congo Hemorrhagic Fever Virus- An Overview


Crimean-Congo Hemorrhagic Fever Virus (CCHFV) is a tick-borne virus that belongs to the family Bunyaviridae and the genus Nairovirus. It is the causative agent of a severe and often fatal disease in humans, known as Crimean-Congo Hemorrhagic Fever (CCHF).

CCHFV has a spherical shape and measures approximately 90 to 120 nm in diameter with 5-10 nm projections visible on the surface. These projections are formed by two glycoproteins, Gn and Gc, which are responsible for receptor binding and entry into host cells. CCHFV is an enveloped virus, meaning it has a lipid bilayer membrane that surrounds its nucleocapsid.

The nucleocapsid of CCHFV contains a tripartite, segmented, negative-sense RNA genome. The genome consists of three segments: large (L), medium (M) and small (S), which are associated with proteins to form ribonucleoproteins (RNPs). The L segment encodes the RNA-dependent RNA polymerase (RdRp), which is involved in transcription and replication of the viral RNA. The M segment encodes the glycoproteins Gn and Gc, as well as a non-structural protein GP38, which is secreted by infected cells and has an unknown function. The S segment encodes the nucleoprotein (N), which binds to the viral RNA and forms the core of the nucleocapsid.

The genome segments of CCHFV have terminal, complementary nucleotide sequences that are conserved among nairoviruses. These sequences serve as promoters for the RdRp and also facilitate the packaging and reassortment of the segments during viral assembly.

The structure of CCHFV is shown in Figure 1.

Figure 1: Structure of CCHFV. Source: Nature Reviews Microbiology