Crimean-Congo haemorrhagic fever virus

Crimean–Congo hemorrhagic fever (CCHF) is a viral disease. Symptoms of CCHF may include fever, muscle pains, headache, vomiting, diarrhea, and bleeding into the skin. Onset of symptoms is less than two weeks following exposure. Complications may include liver failure. In those who survive, recovery generally occurs around two weeks after onset. Crimean–Congo hemorrhagic fever (CCHF) is a viral disease. Symptoms of CCHF may include fever, muscle pains, headache, vomiting, diarrhea, and bleeding into the skin. Onset of symptoms is less than two weeks following exposure. Complications may include liver failure. In those who survive, recovery generally occurs around two weeks after onset. The CCHF virus is typically spread by tick bites or contact with livestock carrying the disease. Those affected are often farmers or work in slaughterhouses. The virus can also spread between people via body fluids. Diagnosis is by detecting antibodies, the virus's RNA, or the virus itself. It is a type of viral hemorrhagic fever. Prevention involves avoiding tick bites. A vaccine is not commercially available. Treatment is typically with supportive care. The medication ribavirin may also help. It occurs in Africa, the Balkans, the Middle East, and Asia. Often it occurs in outbreaks. In 2013 Iran, Russia, Turkey, and Uzbekistan documented more than fifty cases. The risk of death among those affected is between 10 and 40%. It was first detected in the 1940s. The illness in humans is a severe form of hemorrhagic fever. Typically, after a 1–3 day incubation period following a tick bite or 5–6 days after exposure to infected blood or tissues, flu-like symptoms appear, which may resolve after one week. In up to 75% of cases, signs of bleeding can appear within 3–5 days of the onset of illness in case of bad containment of the first symptoms: mood instability, agitation, mental confusion and throat petechiae; and soon after nosebleeds, vomiting, and black stools. The liver becomes swollen and painful. Disseminated intravascular coagulation may occur, as well as acute kidney failure, shock, and sometimes acute respiratory distress syndrome. People usually begin to recover 9–10 days after first symptoms appear. Up to 30% of infected people die by the end of the second week of illness. The Crimean-Congo hemorrhagic fever orthonairovirus (CCHFV) is a member of the genus Orthonairovirus, family Nairoviridae of RNA viruses. The virons are 80–120 nanometers (nm) in diameter and are pleomorphic. There are no host ribosomes within the viron. Each virion contains three copies of the genome. The envelope is single layered and is formed from a lipid bilayer 5 nm thick. It has no protrusions. The envelope proteins form small projections ~5–10 nm long. The nucleocapsids are filamentous and circular with a length of 200–3000 nm.The virus might enter a cell using the cell surface protein nucleolin. The genome is circular, negative sense RNA in three parts – Small (S), Medium (M) and Large (L). The L segment is 11–14.4 kilobases in length while the M and S segments are 4.4–6.3 and 1.7–2.1 kilobases long respectively. The L segment encodes the RNA polymerase, the M segment encodes the envelope glycoproteins (Gc and Gn), and the S segment encodes the nucleocapsid protein. The mutation rates for the three parts of the genome were estimated to be: 1.09×10−4, 1.52×10−4 and 0.58×10−4 substitutions/site/year for the S, M, and L segments respectively. CCHFV is the most genetically diverse of the arboviruses: Its nucleotide sequences frequently differ between different strains, ranging from a 20% variability for the viral S segment to 31% for the M segment. Viruses with diverse sequences can be found within the same geographic area; closely related viruses have been isolated from widely separated regions, suggesting that viral dispersion has occurred possibly by ticks carried on migratory birds or through international livestock trade. Reassortment among genome segments during coinfection of ticks or vertebrates seems likely to have played a role in generating diversity in this virus.