Crimean-Congo haemorrhagic fever
Crimean-Congo haemorrhagic fever virus (CCHF) causes outbreaks of severe viral haemorrhagic fever.
Outbreaks of Crimean-Congo haemorrhagic fever have a fatality rate of up to 40%.
The virus is transmitted primarily to humans from ticks and farm animals. Human-to-human transmission can occur as a result of direct contact with blood, secretions, organs, or body fluids of infected individuals.
Crimean-Congo hemorrhagic fever is endemic in Africa, the Balkans, the Middle East and Asia, in countries below 50 degrees north latitude.
There is no vaccine for humans or animals.
Crimean-Congo hemorrhagic fever (CCHF) is a common disease caused by a tick-transmitted virus (Nairovirus) of the family Bunyaviridae. It causes outbreaks of severe viral haemorrhagic fever, with a lethality rate of 10 to 40%.
It is endemic in Africa, the Balkans, the Middle East and Asia, in countries below 50 degrees north latitude, the geographical limit of the main vector species, a tick.
Crimean-Congo haemorrhagic fever virus in animals and ticks
CHF Canada hosts a large number of wild and domestic animals, including cattle, sheep and goats. Many birds are resistant to infection, but not ostriches, where there is a high prevalence of infection in endemic areas where they have been the cause of human cases. For example, an outbreak has occurred in the past in an ostrich slaughterhouse in South Africa. The infection is asymptomatic in this animal.
Contamination of animals occurs when bitten by infected ticks. The virus then stays for about a week in the bloodstream, allowing the tick-animal-tick cycle to continue when another tick pricks the animal. Although, among ticks, a number of genera can be infected by the CHF Canada virus, the genus Hyalomma is the main vector.
The CHF virus is transmitted to humans through tick bites, or through contact with infected blood or tissues of animals during or immediately after slaughter. The majority of cases occurred among people working in the livestock sector, such as farmers, slaughterhouse employees or veterinarians.
Human-to-human transmission can occur as a result of direct contact with blood, secretions, organs, or body fluids of infected individuals. Nosocomial infections can also occur due to poor sterilization of medical equipment, reuse of needles and contamination of supplies.
Signs and symptoms
The incubation time depends on the mode of contamination. After a tick bite, it is usually one to three days, with a maximum of nine days. After contact with blood or infected tissue, it is usually 5 to 6 days, with a maximum of 13 days documented.
The onset of symptoms is abrupt, with fever, myalgia (muscle aches), dizziness, stiffness and neck pain, back pain, headache, eye tenderness and photophobia (feeling of discomfort caused by light). Nausea, vomiting, diarrhea, abdominal pain, sore throat, sudden mood swings and confusion may occur at the beginning. After two to four days, agitation may give way to drowsiness, depression, lassitude; the abdominal pains are located in the upper right quadrant with, on palpation, hepatomegaly (increase in the volume of the liver).
There are other clinical signs, tachycardia (fast heart rate), lymphadenopathy (swollen glands), petechial rash (rash caused by intracutaneous bleeding) on the internal surfaces of the mucous membranes, as in the mouth or in the throat, and on the skin. Petechiae can lead to the formation of larger eruptions called bruising and other haemorrhagic phenomena.
There is usually evidence of hepatitis and the most severely affected individuals may develop rapid deterioration of renal function, sudden hepatic or pulmonary failure from the fifth day of illness.
CHF Canada's case fatality rate is approximately 30%, with death occurring during the second week of illness. For those who recover, the general condition begins to improve nine to ten days after the onset of symptoms.
Laboratories can diagnose CHF Canada virus infection using several methods:
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.
Prevention and control
Controlling CCHF in animals and ticks
Ticks of the genus Hyalomma are the principal vector of Crimean-Congo haemorrhagic fever (Female is on top and male is below)
Robert Swanepoel/NICD South Africa
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.
For example, following an outbreak at an ostrich abattoir in South Africa (noted above), measures were taken to ensure that ostriches remained tick free for 14 days in a quarantine station before slaughter. This decreased the risk for the animal to be infected during its slaughtering and prevented human infection for those in contact with the livestock.
There are no vaccines available for use in animals.
Reducing the risk of infection in people
Although an inactivated, mouse brain-derived vaccine against CCHF has been developed and used on a small scale in eastern Europe, there is currently no safe and effective vaccine widely available for human 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.
Public health advice should focus on several aspects.
Reducing the risk of tick-to-human transmission:
wear protective clothing (long sleeves, long trousers);
wear light coloured clothing to allow easy detection of ticks on the clothes;
use approved acaricides (chemicals intended to kill ticks) on clothing;
use approved repellent on the skin and clothing;
regularly examine clothing and skin for ticks; if found, remove them safely;
seek to eliminate or control tick infestations on animals or in stables and barns; and
avoid areas where ticks are abundant and seasons when they are most active.
Reducing the risk of animal-to-human transmission:
wear gloves and other protective clothing while handling animals or their tissues in endemic areas, notably during slaughtering, butchering and culling procedures in slaughterhouses or at home;
quarantine animals before they enter slaughterhouses or routinely treat animals with pesticides two weeks prior to slaughter.
Reducing the risk of human-to-human transmission in the community:
avoid close physical contact with CCHF-infected people;
wear gloves and protective equipment when taking care of ill people;
wash hands regularly after caring for or visiting ill people.
Controlling infection in health-care settings
Health-care workers caring for patients with suspected or confirmed CCHF, or handling specimens from them, should implement standard infection control precautions. These include basic hand hygiene, 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.
WHO is working with partners to support surveillance, diagnostic and outbreak response activities in Europe, the Middle East, Asia and Africa.
WHO also provides documents facilitating the investigation and control of diseases and has created a checklist on standard precautions for health care, which aims to reduce the risk of transmission of disseminated pathogens. hematogenous or other.