Crimean-Congo Hemorrhagic Fever (CCHF) is a serious viral disease transmitted primarily by ticks. This illness can lead to severe outbreaks and is known for its high fatality rate, which can range from 10% to 40%. The virus responsible for CCHF belongs to the Nairovirus genus within the Bunyaviridae family.
How the Virus Spreads
The CCHF virus is primarily transmitted to humans through the bites of infected ticks, particularly those of the Hyalomma genus. These ticks act as both vectors and reservoirs. Ticks become infected when they feed on the blood of infected animals, often livestock such as cattle, sheep, and goats.
Infected animals usually do not show signs of illness, but the virus can remain in their bloodstream for about a week. Humans can also contract the virus through direct contact with the blood or tissues of infected animals, especially during slaughter. Occupations like farming, veterinary work, and slaughterhouse operations are high-risk.
Human-to-human transmission is also possible through close contact with the blood, secretions, organs, or other bodily fluids of infected individuals. This can lead to hospital-acquired infections if proper sterilization of medical equipment is not followed or if needles are reused. Healthcare personnel are at elevated risk.
Signs and Symptoms
The clinical presentation of CCHF can vary, but it begins suddenly. Following a tick bite, the incubation period is 1 to 3 days, with a maximum of 9 days. If the infection occurs through contact with infected blood or tissues, the incubation period is 5 to 6 days, extending up to 13 days.
The initial pre-hemorrhagic phase is characterized by non-specific, flu-like symptoms, including sudden fever, muscle aches, dizziness, neck pain and stiffness, backache, headache, sore eyes, and sensitivity to light. Patients may also experience nausea, vomiting, diarrhea, abdominal pain, and a sore throat early in the illness.
As the disease progresses, often after 2 to 4 days, the initial agitation can be replaced by sleepiness, depression, and lassitude. Abdominal pain may localize to the upper right side, and liver enlargement can be detected. The disease can then advance to a hemorrhagic phase, marked by signs such as petechiae (small red spots on the skin due to bleeding), ecchymoses (larger areas of bruising), nosebleeds, and bleeding from the gums. Internal bleeding is also possible, and severely ill patients may experience rapid kidney deterioration, sudden liver failure, or pulmonary failure after the fifth day of illness.
Diagnosis and Treatment
Diagnosis of CCHF considers a patient’s clinical presentation, especially if symptoms suggest hemorrhagic fever. Laboratory tests confirm the CCHF virus. Molecular methods, such as reverse transcription polymerase chain reaction (RT-PCR), are used for rapid diagnosis in the acute phase.
Serological tests, such as Enzyme-Linked Immunosorbent Assay (ELISA), can detect specific antibodies (IgM and IgG) against the virus about 7 days after symptom onset. Diagnosing CCHF can be challenging due to the non-specific nature of its initial symptoms.
Treatment for CCHF is primarily supportive, focusing on managing symptoms and maintaining bodily functions. This includes monitoring and managing fluid and electrolyte balance, ensuring adequate oxygenation, and providing hemodynamic support. Blood transfusions may be necessary for patients experiencing severe bleeding.
The antiviral drug ribavirin has been used in some cases, administered early after symptom onset to prevent severe infection or as a post-exposure measure. While some observational studies suggest a benefit, its clinical efficacy remains a subject of ongoing research, with some studies showing no significant impact on prognosis or hospitalization duration.
Preventing Transmission
Preventing CCHF infection involves personal protective measures and public health interventions. Individuals in endemic areas, particularly those involved in outdoor activities or working with livestock, should take precautions against tick bites. This includes wearing protective clothing that minimizes skin exposure and using tick repellents containing DEET or permethrin on exposed skin and clothing.
After spending time in tick-infested areas, check for and promptly remove any attached ticks using tweezers, grasping the tick close to the skin and pulling it straight out without twisting. For those handling livestock or animal products, wearing gloves and other protective clothing is recommended, especially during slaughtering and butchering. Treating animals with acaricides (chemicals that kill ticks) before slaughter can reduce the risk of transmission.
Strict infection control measures are important for healthcare workers. This includes using personal protective equipment such as gloves, respiratory masks, waterproof gowns, and goggles when caring for suspected or confirmed CCHF patients. Proper disposal of contaminated waste and isolation of patients are necessary to prevent human-to-human transmission in healthcare settings.
Where the Virus is Found
The CCHF virus is found across a wide geographical range, with its distribution linked to the presence of its primary tick vectors, particularly Hyalomma ticks. The disease is endemic in many parts of Africa, the Balkans, the Middle East, and Asia. In Europe, sporadic cases and outbreaks have been reported in countries such as Spain, Russia, and Turkey.
The virus’s presence is influenced by environmental factors that support tick populations. Outbreaks often show seasonal patterns, with cases increasing during warmer months when tick activity is higher. For example, in some regions, cases appear in March, peak in July, and decline by October. The movement of infected ticks by migratory birds can introduce the virus into new areas.