Factsheet about Crimean-Congo haemorrhagic fever
Crimean-Congo haemorrhagic fever (CCHF) is a tick-borne viral disease with symptoms such as high fever, muscle pain, dizziness, abnormal sensitivity to light, abdominal pain and vomiting. Later on, sharp mood swings may occur, and the patient may become confused and aggressive.
CCHF virus is widespread and evidence for the virus has been found among ticks in Africa, Asia, the Middle East and Eastern Europe and South Western Europe.
In Europe cases of human infections have been reported from Albania, Armenia, Bulgaria, Kazakhstan, Kosovo, Russia, Serbia, Tajikistan, Turkey, Turkmenistan, Ukraine, and Uzbekistan. In June 2008, a first case was diagnosed in Greece and Spain reported the first locally acquired case in August 2016.
Crimean-Congo haemorrhagic fever (CCHF) is a viral infection described in parts of Africa, Asia, south-eastern Europe, and the Middle East. The causative agent, CCHF virus, belongs to the genus Nairovirus of the Bunyaviridae family. It causes severe disease in humans with a risk of nosocomial transmission and a high fatality rate. The occurrence of the disease is linked to the geographical distribution of hard tick vectors, mostly from the Hyalomma genus. The name of the virus is linked to the clinical recognition of the disease to Crimea in 1944 and the first isolation of the virus in Congo in 1956. The geographic range of CCHF virus is known to be the most extensive of the tickborne viruses relevant to human health. In Europe, cases have been reported in Albania, Bulgaria, Kosovo, Turkey and the former Soviet Union. In Greece, the first human case of CCHF infection was reported in the summer of 2008. The first human case of CCHF infection was reported in Greece in June 2008. In Spain the first human case of CCHF infection was reported in August 2016 and resulted in a nosocomial infection case.
2. Clinical features and sequelae
After an incubation period, usually of 3–7 days (ranging from 1 to 13 days), the disease is characterised by a sudden onset of febrile illness with headache, myalgia, backache, joint and abdominal pain and vomiting. This is frequently followed by haemorrhagic manifestations that may range from petechiae to ecchymoses appearing on the mucous membranes and the skin; the most common bleeding sites are the nose, gastrointestinal system, uterus, and urinary and respiratory tracts. Necrotic hepatitis may occur. Large ecchymosis and uncontrolled bleeding from venipuncture sites are common features. The convalescent period begins in survivors about 10–20 days after the onset of illness. The length of the incubation period varies depending on several factors, including the viral dose and the route of exposure, and is often shorter following nosocomial infection.
Crimean-Congo haemorrhagic fever virus circulates in a silent enzootic tick-vertebrate-tick cycle, and there is no evidence that the virus causes any disease in animals. Ticks from the Hyalomma genus are the principal vectors of CCHF virus; Hyalomma marginatum is the main vector for CCHF in southern Europe; the virus has also been identified in Hyalomma lusitanicum in Spain. Hares and hedgehogs act as amplifying hosts for the immature stages of the ticks. Domestic animals (cattle, goats, sheep, etc.) are the usual hosts for the adult ticks. Humans are not the preferred hosts of Hyalomma ticks and are infrequently bitten compared to livestock. When infected, ticks can transmit CCHF virus throughout their life. In the northern hemisphere, Hyalomma marginatum is usually activated by the increasing temperature in spring (beginning of April), and the immature stages are active in summer between May and September.
Humans become infected through bites of infected ticks or by contact with infected blood or other livestock tissue. Nosocomial transmission may occur through direct contact with infected blood or body fluids, or through contaminated medical equipment or supply.
Major risk groups include farmers, veterinarians and abattoir workers in endemic areas, and most of the affected cases deal with agriculture and/or domestic animal husbandry and slaughtering activities. Meat itself is not the source of infection because the virus is inactivated by post-slaughter acidification of the tissue, and CCHF virus does not survive cooking. Healthcare workers are the second most affected group when nursing CCHF patients with severe bleeding and haemorrhages in a hospital setting without strict barrier nursing procedures. Outdoor activities in endemic areas are a risk factor for tick exposure.
4. Prevention methods
Prevention and control of CCHF infection is achieved by avoiding or minimising exposure to infected ticks by using tick repellents. Wearing protective clothing and early and correct removal of ticks are recommended. Since nosocomial cases of CCHF are quite common and often result in high mortality, strict universal precautions, including barrier nursing, should be taken with hospitalised cases, as with other haemorrhagic fevers. A vaccine derived from inactivated mouse brain is used in Bulgaria, but is not widely available, and efficiency and safety have to be re-evaluated, as well as specific human immunoglobulin used for post-exposure prophylaxis. In endemic areas, a measure of tick control has been achieved by environmental sanitation of underbrush habitats. Acaricides may be useful on domestic animals to control CCHF virus-infected ticks if used 10–14 days prior to slaughter or to export of animals from enzootic regions.
Direct diagnosis of CCHF is done by detection of viral genome by RT-PCR up to 10–15 days post onset of illness. Serological detection of specific IgM antibodies can be done starting day five. Crimean-Congo haemorrhagic fever IgG seroconversion or four-fold titer increase can help the diagnosis, but it is delayed. As CCHF is considered a highly hazardous pathogen, sample shipment and handling require specific protocols.
5. Management and treatment
Since there is no validated specific antiviral therapy for CCHF, treatment relies on supportive care, including the administration of thrombocytes, fresh frozen plasma, and erythrocyte preparations. Oral or intravenous ribavirin has been used with reported success, although with no confirmed benefit. The value of human immunoglobulins from recovered patients for treatment has to be re-evaluated.
6. Key areas of uncertainty
The understanding of the cycle of CCHF virus transmission needs further field investigations, especially in Europe. There is a lack of standardisation of case definitions, laboratory diagnosis procedures, reporting and documentation of the disease. Treatment with ribavirin is recommended by the World Health Organization, but while many reports indicate that the drug may be beneficial, the real efficacy would require additional evaluation. There is no safe and effective human vaccine available and no animal model exists to test new drugs and/or vaccines.
Note: The information contained in this factsheet is intended for the purpose of general information and should not be used as a substitute for the individual expertise and judgement of healthcare professionals.
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