Crimean-Congo haemorrhagic fever (CCHF)
Crimean-Congo haemorrhagic fever is a viral haemorrhagic fever transmitted by ticks. It can be responsible for serious epidemics in humans, but it is not pathogenic for ruminants, their amplifying host.
The disease was described for the first time in Crimea in 1944 as Crimean haemorrhagic fever. In 1969, it was recognized that the pathogen responsible for Crimean haemorrhagic fever was the same as that responsible for a disease identified in 1956 in Congo, and the coupling of the two place names gave the current name of the disease. disease and the virus.
Crimean-Congo haemorrhagic fever (CCHF) spreads to humans either by tick-bites, or through contact with viraemic animal tissues during and immediately post-slaughter. CCHF outbreaks constitute a threat to public health services because of its epidemic potential, its high case fatality ratio (10-40%), its potential for nosocomial outbreaks and the difficulties in treatment and prevention. CCHF is endemic in all of Africa, the Balkans, the Middle East and in Asia.
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 13 days.
Onset of symptoms is sudden, with fever, myalgia, (muscle ache), dizziness, neck pain and stiffness, 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 two to four 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.
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.
CCHF virus infection can be diagnosed by several different laboratory tests:
Enzyme-linked immunosorbent assay (ELISA);
Reverse transcriptase polymerase chain reaction (RT-PCR) assay; and
Virus isolation by cell culture.
Patients with fatal disease, as well as in patients in the first few days of illness, do not usually develop a measurable antibody response and so diagnosis in these individuals is achieved by virus or RNA detection in blood or tissue samples.
Tests on patient samples present an extreme biohazard risk and should only be conducted under maximum biological containment conditions. However, if samples have been inactivated (e.g. with virucides, gamma rays, formaldehyde, heat, etc.), they can be manipulated in a basic biosafety environment.
General supportive care with treatment of symptoms is the main approach to managing 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.
Control of CCHF in animals and ticks
It is difficult to prevent or control CCHF infection in animals and ticks because the tick-animal-tick cycle usually goes unnoticed and infection in domestic animals is usually not apparent. In addition, since tick vectors are numerous and widespread, control of ticks with acaricides (chemicals used to kill ticks) is only a realistic option for well-managed animal production facilities.
There are no vaccines available for use in animals.
Reduce the risk of infection in humans
Although an inactivated vaccine derived from the brain of mice and against CHF C was developed and used on a small scale in Eastern Europe, there is currently no safe and effective vaccine widely available for human consumption.
In the absence of a vaccine, the only way to reduce infection in people is to increase awareness of risk factors and to educate people on how to reduce exposure to the virus.
Controlling infection in a healthcare setting
Health care workers who care for, or handle specimens from, suspected or confirmed CHF patients should follow the standard infection control precautions. These include basic hand hygiene, the use of personal protective equipment, safe injection practices and safe burial practices.
As a precaution, health care workers who care for patients immediately outside the FHCC outbreak area should also apply standard precautions for infection control.
Samples taken from persons suspected of FHCC should be handled by qualified personnel working in well-equipped laboratories.
Recommendations for infection control in the management of patients with suspected or confirmed Crimean-Congo haemorrhagic fever should follow those developed by WHO for Ebola and Marburg haemorrhagic fever.