Crimean-Congo Haemorrhagic Fever (Human)

Primary reference(s)

WHO, 2013. Crimean-Congo haemorrhagic fever. World Health Organization (WHO). Accessed 6 November 2020.

Additional scientific description

The Crimean-Congo haemorrhagic fever (CCHF) virus is a tick-borne virus (Nairovirus) of the Bunyaviridae family. The hosts of the CCHF virus include a wide range of wild and domestic animals such as cattle, sheep and goats. Many birds are resistant to infection, but ostriches are susceptible and may show a high prevalence of infection in endemic areas, where they have been at the origin of human cases. There is no apparent disease in these animals (WHO, 2013).

The CCHF virus is transmitted to humans either by tick bites (principally ticks of the genus Hyalomma) or through contact with infected animal blood or tissues during and immediately after slaughter. Human-to-human transmission can occur from close contact with the blood, secretions, organs or other bodily fluids of infected persons. Hospital-acquired infections can also occur due to improper sterilisation of medical equipment and reuse of non-sterile needles (WHO, 2013).

The length of the incubation period depends on the mode of acquisition of the virus. Following infection by a tick bite, the incubation period is usually one to three days, with a maximum of nine days. The incubation period following contact with infected blood or tissues is usually five to six days, with a documented maximum of thirteen days (WHO, 2013).

The disease begins with a sudden onset of influenza-like symptoms which may progress to severe bleeding and death if not treated. The case-fatality rate is 10–40% (WHO, 2019a).

Laboratory diagnosis is via serological and virological testing, either detecting the microorganism itself, or the antibodies produced by the body in response to the infection (WHO, 2013).

The disease was first described in the Crimea in 1944 and given the name Crimean haemorrhagic fever. In 1969 it was recognised that the pathogen causing Crimean haemorrhagic fever was the same as that responsible for an illness identified in 1956 in the Congo. The linkage of the two place names resulted in the current name for the disease and the virus.

Metrics and numeric limits

Crimean-Congo haemorrhagic fever is endemic in Africa, the Balkans, the Middle East and Asian countries south of the 50th parallel north – the current geographical limit of the principal tick vector. There are an estimated 3 billion people at risk, with an estimated 10,000 to 15,000 infections annually (WHO, 2018).

The European Centre for Disease Prevention and Control (ECDC) has published case definitions on Crimean-Congo haemorrhagic fever prevention and control (ECDC, 2008).

Examples of drivers, outcomes and risk management

Containing and preventing outbreaks of CCHF is difficult because of the lack of a safe and effective vaccine (for humans and animals), the widespread presence of tick vectors, and the fact that the infection mostly goes unnoticed in domestic animals. The focus is therefore on awareness and education efforts with regards to reducing transmission risk (WHO, 2019b).

Outbreaks of CCHF constitute a threat to public health services because the virus can lead to epidemics, has a high case fatality ratio (10–40%), potentially results in hospital and health facility outbreaks, and is difficult to prevent and treat (WHO, 2019a).