Fact Sheet No 208
Revised November 2001
CRIMEAN-CONGO HAEMORRHAGIC FEVER
Crimean-Congo haemorrhagic fever (CCHF) is a viral
haemorrhagic fever of the Nairovirus group. Although primarily a
zoonosis, sporadic cases and outbreaks of CCHF affecting humans do
occur. The disease is endemic in many countries in Africa, Europe and
Asia, and during 2001, cases or outbreaks have been recorded in Kosovo,
Albania, Iran, Pakistan, and South Africa.
The disease was first described in the Crimea 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, and
linkage of the 2 place names resulted in the current name for the
disease and the virus. CCHF is a severe disease in humans, with a high
mortality rate. Fortunately, human illness occurs infrequently, although
animal infection may be more common.
The geographical distribution of the virus, like that
of its tick vector, is widespread. Evidence of CCHF virus has been found
in Africa, Asia, the Middle East and Eastern Europe. Healthcare workers
in endemic areas should be aware of the illness and the correct
infection control procedures to protect themselves and their patients
from the risk of nosocomial (hospital-acquired) infection.
The virus which causes CCHF is a Nairovirus, a
group of related viruses forming one of the five genera in the Bunyaviridae
family of viruses. All of the 32 members of the Nairovirus genus
are transmitted by argasid or ixodid ticks, but only three have been
implicated as causes of human disease: the Dugbe and Nairobi sheep
viruses, and CCHF, which is the most important human pathogen amongst
CCHF Reservoirs and Vectors
- The CCHF virus may infect a wide range of domestic and wild
animals. Many birds are resistant to infection, but ostriches are
susceptible and may show a high prevalence of infection in endemic
areas. Animals become infected with CCHF from the bite of infected
- A number of tick genera are capable of becoming infected with CCHF
virus, but the most efficient and common vectors for CCHF appear to
be members of the Hyalomma genus. Trans-ovarial (transmission
of the virus from infected female ticks to offspring via eggs) and
venereal transmission have been demonstrated amongst some vector
species, indicating one mechanism which may contribute to
maintaining the circulation of the virus in nature.
- However, the most important source for acquisition of the virus by
ticks is believed to be infected small vertebrates on which immature
Hyalomma ticks feed. Once infected, the tick remains infected
through its developmental stages, and the mature tick may transmit
the infection to large vertebrates, such as livestock. Domestic
ruminant animals, such as cattle, sheep and goats, are viraemic
(virus circulating in the bloodstream) for around one week after
- Humans who become infected with CCHF acquire the virus from direct
contact with blood or other infected tissues from livestock during
this time, or they may become infected from a tick bite. The
majority of cases have occurred in those involved with the livestock
industry, such as agricultural workers, slaughterhouse workers and
- The length of the incubation period for the illness appears to
depend on the mode of acquisition of the virus. Following infection
via 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 13 days.
- Onset of symptoms is sudden, with fever, myalgia (aching muscles),
dizziness, neck pain and stiffness, backache, headache, sore eyes
and photophobia (sensitivity to light). There may be nausea,
vomiting and sore throat early on, which may be accompanied by
diarrhoea and generalised abdominal pain. Over the next few days,
the patient may experience sharp mood swings, and may become
confused and aggressive. After two to four days, the agitation may
be replaced by sleepiness, depression and lassitude, and the
abdominal pain may localize to the right upper quadrant, with
detectable hepatomegaly (liver enlargement).
- Other clinical signs which emerge include tachycardia (fast heart
rate), lymphadenopathy (enlarged lymph nodes), and a petechial rash
(a rash caused by bleeding into the skin), both on internal mucosal
surfaces, such as in the mouth and throat, and on the skin. The
petechiae may give way to ecchymoses (like a petechial rash, but
covering larger areas) and other haemorrhagic phenomena such as
melaena (bleeding from the upper bowel, passed as altered blood in
the faeces), haematuria (blood in the urine), epistaxis (nosebleeds)
and bleeding from the gums. There is usually evidence of hepatitis.
The severely ill may develop hepatorenal (i.e., liver and kidney)
and pulmonary failure after the fifth day of illness.
- The mortality rate from CCHF is approximately 30%, with death
occurring in the second week of illness. In those patients who
recover, improvement generally begins on the ninth or tenth day
after the onset of illness.
- Diagnosis of suspected CCHF is performed in specially-equipped,
high biosafety level laboratories. IgG and IgM antibodies may be
detected in serum by enzyme-linked immunoassay (the
"ELISA" or "EIA" methods) from about day six of
illness. IgM remains detectable for up to four months, and IgG
levels decline but remain detectable for up to five years.
- Patients with fatal disease do not usually develop a measurable
antibody response and in these individuals, as well as in patients
in the first few days of illness, diagnosis is achieved by virus
detection in blood or tissue samples. There are several methods for
doing this. The virus may be isolated from blood or tissue specimens
in the first five days of illness, and grown in cell culture. Viral
antigens may sometimes be shown in tissue samples using
immunofluorescence or EIA.
- More recently, the polymerase chain reaction (PCR), a molecular
method for detecting the viral genome, has been successfully applied
- General supportive therapy is the mainstay of patient management
in CCHF. Intensive monitoring to guide volume and blood component
replacement is required.
- The antiviral drug ribavirin has been used in treatment of
established CCHF infection with apparent benefit. Both oral and
intravenous formulations seem to be effective.
- The value of immune plasma from recovered patients for therapeutic
purposes has not been demonstrated, although it has been employed on
Prevention and Control
- Although an inactivated, mouse brain-derived vaccine against CCHF
has been developed and used on a small scale in Eastern Europe,
there is no safe and effective vaccine widely available for human
use. The tick vectors are numerous and widespread and tick control
with acaricides (chemicals intended to kill ticks) is only a
realistic option for well-managed livestock production facilities.
- Persons living in endemic areas should use personal protective
measures that include avoidance of areas where tick vectors are
abundant and when they are active (Spring to Fall); regular
examination of clothing and skin for ticks, and their removal; and
use of repellents.
- Persons who work with livestock or other animals in the endemic
areas can take practical measures to protect themselves. These
include the use of repellents on the skin (e.g. DEET) and clothing
(e.g. permethrin) and wearing gloves or other protective clothing to
prevent skin contact with infected tissue or blood.
- When patients with CCHF are admitted to hospital, there is a risk
of nosocomial spread of infection. In the past, serious outbreaks
have occurred in this way and it is imperative that adequate
infection control measures be observed to prevent this disastrous
- Patients with suspected or confirmed CCHF should be isolated and
cared for using barrier nursing techniques. Specimens of blood or
tissues taken for diagnostic purposes should be collected and
handled using universal precautions. Sharps (needles and other
penetrating surgical instruments) and body wastes should be safely
disposed of using appropriate decontamination procedures.
- Healthcare workers are at risk of acquiring infection from sharps
injuries during surgical procedures and, in the past, infection has
been transmitted to surgeons operating on patients to determine the
cause of the abdominal symptoms in the early stages of (at that
moment undiagnosed) infection. Healthcare workers who have had
contact with tissue or blood from patients with suspected or
confirmed CCHF should be followed up with daily temperature and
symptom monitoring for at least 14 days after the putative exposure.
For more detailed information on CCHF, consult the
following chapter: Nairovirus Infections, by R. Swanepoel, in
Exotic Viral Infections, ed. J.S. Porterfield, London, 1995.
Helpful web-based resources include: All the Virology on the World-Wide
Web (www.etc) which provides information and links to numerous web-based