Crimean-Congo haemorrhagic fever: origins, reservoirs, transmission and guidelines
Source: gov.uk (2025-12-01)

Crimean-Congo haemorrhagic fever (CCHF) is a viral haemorrhagic fever (VHF) caused by a virus of the Nairoviridae family.

CCHF is a tick-borne disease which cycles between a wide range of domestic and wild animals, with humans infected via tick bites or contact with infected blood and tissues. It is not present in the United Kingdom (UK), nor are there any identified established populations of Hyalomma ticks, the principal vectors of CCHF virus (CCHFV).

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. Humans (and possibly non-human primates) are the only animal species known to manifest severe clinical CCHF disease.

Epidemiology

CCHF has a widespread geographical distribution (see below maps and the HCID: country specific risk webpage (https://www.gov.uk/guidance/high-consequence-infectious-disease-country-specific-risk)). It is considered endemic in countries in Africa, the Balkans, the Middle East, and western and south-central Asia. It is estimated that globally between 10,000 and 15,000 human infections, including approximately 500 fatalities, occur annually, although this is likely to be an underestimate as many cases may be subclinical or unrecognised.

The global distribution of human cases corresponds to the geographical range of established Hyalomma tick species, notably H. marginatum and H. lusitanicum, which are considered the primary vectors of CCHFV. These ticks commonly infest livestock and other animals. Although small mammals are involved in the disease cycle, the principal reservoir are ticks. Ticks can transmit the virus sexually, and to their offspring. 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, but do not show symptoms. Domestic and wild mammals act as disease amplifiers and can transport the disease to adjacent areas. Many bird species carry Hyalomma ticks, but most birds are thought to be relatively resistant to infection with CCHF virus.

Globally, there have been case reports, virological or serological evidence of human infection in at least 55 countries. In the European Region and its neighbouring countries, locally acquired human cases and/or outbreaks have been reported from Albania, Bulgaria, Georgia, Greece, Kosovo, Russia, Spain, Turkey and Ukraine. Spain officially reported its first autochthonous case in August 2016, the first in Western Europe, following their first detection of CCHFV infected ticks in 2010. At the end of October 2023, French officials reported the detection of CCHFV in H. marginatum ticks collected from cattle in the eastern Pyrénées, which was the first time the presence of the virus in tick populations had been confirmed in the country.

Figure 1. Maps of human CCHF cases in (A) Europe, (B) Asia and (C) Africa.

See the HCID: country specific risk webpage (https://www.gov.uk/guidance/high-consequence-infectious-disease-country-specific-risk) for further information.

(A) Europe

(B) Asia

(C) Africa

Transmission

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 animals, usually through slaughter and/or butchering
- contact with the blood, tissues or body fluids of infected humans, usually in a healthcare setting
The majority of cases occur in those living in CCHF-endemic areas with occupational or recreational exposure to livestock, including:
- farmers
- veterinarians
- slaughterhouse workers
- livestock owners
- other people who work with animals
Cases also occur in healthcare workers or others caring for infected persons where adequate infection control precautions have not been taken.

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.

Symptoms

CCHF disease has varying manifestations from asymptomatic or subclinical infection through to haemorrhage and multi-organ failure. The incubation period can be up to 14 days although is usually less (typically 3 to 7 days). The incubation period varies depending on factors including viral dose and route of exposure and is often shorter following nosocomial infection.

Symptomatic illness typically has 3 phases.
- The pre-haemorrhagic phase begins abruptly with a fever accompanied by non-specific symptoms which may include: muscle aches
- dizziness
- neck pain and stiffness
- backache
- headache
- sore eyes and photophobia
- confusion
Nausea, vomiting and sore throat may also occur, with diarrhoea and abdominal pain. The haemorrhagic phase usually begins 3 to 5 days after symptom onset, although can be longer. This phase usually begins with a petechial rash and may then progress to more severe features including:
- bruising
- generalised bleeding of the gums and orifices
- bleeding into the brain and/or the abdomen
- hypotension
- kidney failure
- neurological and neuropsychiatric symptoms such as meningism and confusion
In fatal cases, death occurs from haemorrhage, multi-organ failure and shock usually between days 5 and 14 of illness. In non-fatal cases, the convalescent phase usually starts 10 to 20 days after initial symptoms. Most patients make a full recovery, but some may experience fatigue and malaise for many months.

Reported overall case fatality rates have varied from 5% to more than 40%. It is possible that subclinical infections represent a substantial proportion of cases, thus resulting in under ascertainment of the true number of cases.

Diagnosis

In the UK, clinicians who suspect that a patient may have CCHF should seek urgent advice from the UK Health Security Agency’s (UKHSA) Imported Fever Service (https://www.gov.uk/guidance/imported-fever-service-ifs) (IFS) on xx-xxxx-xxxx. The IFS operates 24/7 and provides advice on risk assessment, immediate management and infection control. The IFS will also coordinate urgent testing at UKHSA’s Rare and Imported Pathogens Laboratory (https://www.gov.uk/government/collections/rare-and-imported-pathogens-laboratory-ripl) (RIPL), Porton. RIPL provides polymerase chain reaction (PCR) testing for CCHF including out of hours if indicated.

See VHF sample testing advice (https://www.gov.uk/government/publications/viral-haemorrhagic-fever-sample-testing-advice).

Treatment

There are currently no licensed vaccines or specific antivirals to treat CCHF. The use of the antiviral ribavirin for treatment may be beneficial, provided it is commenced early in the course of illness but recently the evidence for this has been increasingly challenged and more work is needed to find the best treatment regimen. Ribavirin has also been suggested as post-exposure prophylaxis following percutaneous exposure. Favipiravir has shown good activity in treating bunyavirus infections in laboratory animals, but currently there is no data available on its efficacy in humans. Treatment is therefore mainly supportive and includes:
- replacing blood components
- balancing fluids and electrolytes
- maintaining oxygen status and blood pressure
- organ support as needed
Guidelines

The UK has specialist guidance on the management (including infection control) of patients with viral haemorrhagic fevers (https://www.gov.uk/government/publications/viral-haemorrhagic-fever-algorithm-and-guidance-on-management-of-patients), including CCHF. See more guidance on CCHF contact tracing and epidemiological case definitions. (https://www.gov.uk/government/collections/crimean-congo-haemorrhagic-fever-cchf-contact-tracing)

The guidelines provide advice on risk assessment, testing and management of suspected CCHF cases presenting to healthcare services within the UK.

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. CCHF is a VHF: suspected cases must be immediately isolated and assessed using appropriate VHF assessment personal protective equipment. See the ACDP algorithm and guidance on management of patients (https://www.gov.uk/government/publications/viral-haemorrhagic-fever-algorithm-and-guidance-on-management-of-patients).

In the UK, confirmed cases will be notified immediately to the High Consequence Infectious Diseases Network to arrange urgent transport to a High Level Isolation Unit.

Cases imported into the UK

Confirmed CCHF cases have been imported into the UK, including one fatal case in 2012 and one in 2014.

In March 2022, a CCHF case was reported in the UK following an initial positive test result. However, this case was not confirmed as CCHF on follow-up samples.