Crimean-Congo Hemorrhagic Fever (CCHF) is a widespread viral disease caused by a tick-borne virus. This pathogen, a member of the Nairovirus genus in the Bunyaviridae family, is responsible for severe viral hemorrhagic fever outbreaks. The disease was first identified in the Crimean Peninsula in 1944, and later in the Congo Basin in 1956, leading to its current name after the two pathogens were found to be the same in 1969.
CCHF can cause epidemics and has a high case fatality rate. The geographic distribution of the disease is closely linked to the presence of its primary tick vector. Wild and domestic animals such as cattle, sheep, and goats can act as hosts for the CCHF virus, though they do not show signs of illness.
Transmission Methods
The primary method of CCHF transmission to humans is through the bite of an infected tick or by crushing one with bare hands. Ticks belonging to the Hyalomma genus are the principal vector, and they become infected by feeding on animals that have the virus in their bloodstream. The virus can remain in an animal’s blood for about a week after infection, allowing the tick-animal-tick cycle to perpetuate.
Another route of transmission is from animals to humans through direct contact with the blood or tissues of infected livestock. This mode of transmission is common during and immediately after the slaughter of animals. Individuals involved in the livestock industry, such as agricultural workers, slaughterhouse employees, and veterinarians, are at a higher risk of contracting the disease.
Human-to-human transmission also occurs through close contact with the blood, secretions, organs, or other bodily fluids of an infected individual. This presents a risk in healthcare settings, where infections can occur. Such instances are often the result of improper sterilization of medical equipment, the reuse of needles, or the contamination of medical supplies, requiring stringent infection control measures when caring for patients with CCHF.
Symptoms and Disease Progression
The incubation period for CCHF varies depending on the mode of transmission. Following a tick bite, the incubation period is between one to three days, with a maximum of nine days. If the infection is acquired through contact with infected blood or tissues, the incubation period is longer, ranging from five to six days and extending up to a maximum of 13 days. The onset of symptoms is abrupt and marks the pre-hemorrhagic phase.
Initial symptoms of CCHF include a sudden onset of:
- Fever
- Muscle ache (myalgia)
- Dizziness
- Neck pain and backache
- Headache
- Sore eyes with a sensitivity to light (photophobia)
Some individuals may also experience nausea, vomiting, diarrhea, and a sore throat in the early stages. These non-specific symptoms can be accompanied by sharp mood swings and confusion. After two to four days, this initial agitation may give way to sleepiness and depression.
The hemorrhagic phase begins a few days after the initial onset of symptoms and is characterized by signs of bleeding and vascular instability. Patients may develop petechiae (small red or purple spots on the skin). As the illness progresses, larger bruises and other hemorrhagic phenomena can appear, leading to uncontrolled bleeding from the gums, nose, or other sites.
For those who survive the infection, the recovery process is often slow. Improvement begins around the ninth or tenth day after the initial onset of illness. The recovery period can be prolonged, and patients may experience continued weakness.
Diagnosis and Treatment
Diagnosing CCHF in its early stages is challenging because the initial symptoms are non-specific. A definitive diagnosis requires laboratory testing to detect the virus or antibodies. The most commonly used diagnostic methods include enzyme-linked immunosorbent assay (ELISA), antigen detection tests, and reverse transcriptase-polymerase chain reaction (RT-PCR). These tests can identify the virus’s genetic material or antibodies produced by the immune system.
There is no vaccine available for either humans or animals to prevent CCHF infection. Treatment consists of supportive care to manage symptoms. This includes careful management of fluid and electrolyte levels, ensuring adequate oxygenation, and providing circulatory support to maintain blood pressure. Early supportive care improves survival.
While no specific antiviral medication is approved for CCHF, the drug ribavirin is often used to treat the infection. Its clinical effectiveness is still a subject of ongoing study, but it is most beneficial when administered during the earlier phase of the illness. The case fatality rate for CCHF is estimated to be between 10% and 40%, with death occurring in the second week of illness for fatal cases.
Prevention and Control
Preventing CCHF infection relies on avoiding tick bites, especially in endemic regions. Individuals can reduce their risk by wearing protective clothing that covers the arms and legs. Light-colored clothing is recommended as it makes it easier to spot ticks. Using an approved insect repellent containing DEET on both skin and clothing provides protection. Regularly check for and safely remove ticks from your body and clothing after being in tick-infested areas.
For those in high-risk occupations, such as healthcare workers, livestock farmers, and slaughterhouse workers, occupational precautions are necessary. This includes the use of personal protective equipment (PPE), such as gloves, gowns, and face protection, when handling potentially infected animals or human specimens. Practicing safe handling and disposal of contaminated materials is also necessary for prevention.
Awareness of the geographic areas where CCHF is endemic is important. The disease is found in parts of Eastern Europe, particularly the Balkans, as well as throughout Africa, the Middle East, and Asia. This knowledge helps travelers and residents in these regions take preventive measures. Since the infection in domestic animals is often not apparent, controlling the disease in animals and ticks is difficult.