Crimean‑Congo hemorrhagic fever virus (CCHFV) is a member of the genus Orthonairovirus (family Nairoviridae) and is the aetiological agent of Crimean‑Congo hemorrhagic fever, a severe tick‑borne disease of humans. The virus has a tripartite negative‑sense RNA genome composed of small (S), medium (M) and large (L) segments encoding the nucleoprotein, glycoprotein precursor (processed into Gn and Gc) and RNA‑dependent RNA polymerase. CCHFV virions are enveloped and roughly spherical.
Classification, Ecology and Pathogenesis
CCHFV circulates in an enzootic cycle involving hard ticks, particularly Hyalomma species, and a wide range of wild and domestic vertebrates including cattle, sheep and hares. Ticks serve as both vector and reservoir; transstadial and transovarial transmission maintain the virus in tick populations. Vertebrate hosts develop transient viraemia without apparent illness, allowing ticks to acquire and transmit the virus. Humans become infected through the bite of an infected tick or by contact with blood or tissues from viraemic animals. Nosocomial transmission via exposure to patient blood or body fluids has also been documented. Following infection, CCHFV targets endothelial cells, hepatocytes and immune cells, leading to increased vascular permeability, coagulopathy and multi‑organ failure. The incubation period ranges from 2 to 9 days, after which patients develop sudden fever, myalgia and gastrointestinal symptoms followed by haemorrhagic manifestations. Case fatality rates vary from 10 to 40 %, depending on the outbreak and availability of care. There is no specific antiviral therapy, though ribavirin has been used empirically, and no widely licensed vaccine exists.
Geographic Distribution and Outbreaks
CCHFV has the widest geographic range of any tick‑borne virus, occurring in more than 30 countries across Africa, the Middle East, Asia and southeastern Europe. The virus was first recognized during a 1944‑1945 outbreak among Soviet troops in the Crimea, and a similar virus was isolated in 1956 from a patient in the Belgian Congo; the two were later found to be the same agent. Endemic foci exist in Turkey, Iran, Pakistan, Afghanistan, Iraq, Oman, Russia, Bulgaria and the Balkan region, with seasonal peaks linked to tick activity and livestock movements. Large outbreaks in Turkey since 2002 have resulted in hundreds of cases annually, with nosocomial infections among healthcare workers underscoring the need for stringent barrier precautions. Sporadic cases and clusters have been reported in Greece, Spain and Georgia. Prevention focuses on tick control, use of repellents and protective clothing, safe handling of livestock and strict infection control in hospitals. Crimean‑Congo hemorrhagic fever virus remains a significant public health concern due to its high mortality, broad geographic range and potential for nosocomial spread. Enhanced surveillance, vector control and vaccine research are essential to reduce the burden of this life‑threatening disease. Related Terms: Zaire ebolavirus, Marburg virus, Lassa virus, Rift Valley fever virus, Hantaan virus