Crimean-Congo haemorrhagic fever (CCHF) is a viral haemorrhagic fever (VHF) caused by a virus of the Nairovirus group.
The virus infects a range of domestic and wild animals, and is spread via the bite of an infected tick.
CCHF was first described in the Crimea in 1944, among soldiers and agricultural workers, and in 1969 it was recognised that the virus causing the disease was identical to a virus isolated from a child in the Congo in 1956.
CCHF is endemic in many countries in Africa, the Middle East, Eastern Europe and Asia.
In August 2016, Spain reported its first autochthonous CCHF cases. One was a fatal case which followed a tickbite acquired in the Castilla-Leon region and one was a nosocomial transmission which occurred during care of the first case. Spain had first reported infected ticks in 2010.
Outbreaks have been recorded in Russia, Turkey, Iran, Kazakhstan, Mauritania, Kosovo, Albania, Pakistan, and southern Africa in recent years. Greece reported a single case in 2008.
The global distribution of cases corresponds to those areas where the ticks are found.
Infected Ixodid ticks spread the virus. The most efficient and common vectors appear to be members of the Hyalomma genus, which commonly infest livestock and other animals.
Immature ticks acquire the virus by feeding on infected small animals. Once infected, the tick carries the virus for life, and passes it to animals or humans when it bites them.
Domestic ruminants such as cattle, sheep and goats carry the virus for around one week after becoming infected.
Most birds are thought to be relatively resistant to infection with CCHF virus. Many bird species carry Hyalomma ticks, and human infections have occurred in people working with ostriches.
Cases imported into the UK
Two confirmed CCHF cases have been imported into the UK, one fatal case in 2012 and one in 2014.
Infections pass to humans by:
- the bite of an infected tick
- contamination with tick body contents (for example, if you squash a tick between your fingers)
- direct contact with the blood, tissues or body fluids of infected humans or animals
The majority of cases occur in those living in tick-infested areas with occupational exposure to livestock, including:
- slaughterhouse workers
- livestock owners
- other people who work with animals
Cases also occur in healthcare workers or others caring for infected persons without taking adequate infection control precautions.
CCHF outbreaks are generally associated with a change in situation such as war, population and animal movements, or climatic and vegetation changes which produce more ground cover for small mammals which act as hosts for ticks.
These conditions can lead to explosions in tick populations, and allow increased tick and human contact.
The incubation period of CCHF appears to vary according to the mode of acquisition of the virus.
If a patient has been infected by a tick bite, the incubation period is usually 1 to 3 days, up to 9 days.
Infection via contact with infected blood or tissues leads to an incubation period of 5 to 6 days, and the maximum recorded incubation period is 13 days.
The illness begins abruptly, with:
- muscle aches
- neck pain and stiffness
- sore eyes and photophobia
Nausea, vomiting and sore throat may also occur, with diarrhoea and abdominal pain. More severe symptoms can follow, including:
- petechial rash
- generalised bleeding of the gums and orifices.
In severe cases patients develop multiorgan failure. Approximately 30% of cases are fatal.
In the UK, Public Health England (PHE) has specialised laboratory facilities to provide a definitive diagnosis at PHE Porton.
General supportive therapy is given, including:
- replacing blood components
- balancing fluids and electrolytes
- maintaining oxygen status and blood pressure
There is evidence that CCHF responds to treatment with the antiviral drug ribavirin, in both oral and intravenous formulations.
Prevention and control
There is no licensed vaccine for human use.
Persons living in or visiting endemic areas should use personal protective measures to avoid contact with ticks, including:
- avoiding areas where ticks are abundant at times when they are active
- using tick repellents
- checking clothing and skin carefully for ticks
People who work with livestock or other animals in endemic areas should protect themselves by using tick repellents on their skin and clothing, and wearing gloves or other protective clothing to prevent skin coming into contact with infected tissue or blood.
Serious outbreaks have occurred in the past in hospitals treating patients with CCHF. Hospitals must observe adequate infection control procedures (barrier nursing). Contaminated needles, surgical instruments and body waste materials should be safely disposed of using appropriate decontamination procedures. See ACDP algorithm and guidance on management of patients.