Crimean-Congo haemorrhagic fever (CCHF) is a viral haemorrhagic fever usually transmitted by ticks. It can also be contracted through contact with viraemic animal tissues (animal tissue where the virus has entered the bloodstream) during and immediately post-slaughter of animals. CCHF outbreaks constitute a threat to public health services as 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. CCHF is endemic in all of Africa, the Balkans, the Middle East and in Asia.
The disease was first described in the Crimean Peninsula in 1944 and given the name Crimean haemorrhagic fever. In 1969 it was recognized that the pathogen causing Crimean haemorrhagic fever was the same as that responsible for an illness identified in 1956 in the Congo Basin. The linkage of the two place names resulted in the current name for the disease and the virus.
Following infection by a tick bite, the incubation period of Crimean-Congo haemorrhagic fever (CCHF) is usually 1–3 days, with a maximum of 9 days. Following contact with infected blood or tissues, the incubation period is usually 5–6 days, with a maximum of 13 days.
Onset of symptoms is sudden and can include fever, muscle ache, dizziness, neck pain, backache, headache, sore eyes and photophobia (sensitivity to light). There may be nausea, vomiting, diarrhoea, abdominal pain and sore throat early on, followed by sharp mood swings and confusion. After 2–4 days the agitation may be replaced by sleepiness, depression and lassitude, and the abdominal pain may localize to the upper right quadrant, with detectable hepatomegaly (liver enlargement).
Other clinical signs include tachycardia (fast heart rate), lymphadenopathy (enlarged lymph nodes), and a petechial rash (a rash caused by bleeding into the skin) on internal mucosal surfaces, such as in the mouth and throat, and on the skin. The petechiae may give way to larger rashes called ecchymoses, and other haemorrhagic phenomena. There is usually evidence of hepatitis, and severely ill patients may experience rapid kidney deterioration, sudden liver failure or pulmonary failure after the fifth day of illness.
General supportive care with treatment of symptoms is the main approach to managing Crimean-Congo haemorrhagic fever (CCHF) in people. The antiviral drug ribavirin has been used to treat CCHF infection with apparent benefit. Both oral and intravenous formulations seem to be effective.
The mortality rate from CCHF is approximately 30%, with death occurring in the second week of illness. In patients who recover, improvement generally begins on the ninth or tenth day after the onset of illness.
It is difficult to prevent or control CCHF infection in animals and ticks as the tick-animal-tick cycle usually goes unnoticed and the infection in domestic animals is usually not apparent. Furthermore, the tick vectors are numerous and widespread, so tick control with acaricides (chemicals intended to kill ticks) is only a realistic option for well-managed livestock production facilities.
There are no vaccines widely available for human or animal use. In the absence of a vaccine, the only way to reduce infection in people is by raising awareness of the risk factors and educating people about the measures they can take to reduce exposure to the virus.