Crimean-Congo Hemorrhagic Fever (CCHF), also known as Congo virus, is a serious viral disease. It is caused by the Crimean-Congo Hemorrhagic Fever virus (CCHFV), a tick-borne virus belonging to the Nairovirus genus within the Bunyaviridae family. The disease can lead to severe bleeding and prove fatal.
How the Virus Spreads
The CCHF virus primarily spreads to humans through the bite of infected ticks, particularly Hyalomma ticks, the main vector. Ticks can carry the virus through their life stages and pass it to their offspring. Humans can also contract the virus through direct contact with infected animal blood or tissues, especially during or immediately after slaughter. This risk is elevated for those in the livestock industry, including agricultural workers, slaughterhouse personnel, and veterinarians.
Human-to-human transmission also occurs through close contact with an infected person’s blood, secretions, organs, or other bodily fluids. This spread is a concern in healthcare settings if proper infection control measures are not followed. Improper sterilization of medical equipment, needle reuse, and contaminated medical supplies can contribute to hospital-acquired infections.
Symptoms and Disease Progression
The incubation period for CCHF varies: one to three days after a tick bite (up to nine days), or five to six days after contact with infected blood or tissues (up to 13 days). The onset of symptoms is sudden and marks the beginning of the pre-hemorrhagic phase.
Initial symptoms often include high fever, muscle ache, dizziness, neck pain and stiffness, backache, headache, sore eyes, and light sensitivity. Nausea, vomiting, diarrhea, abdominal pain, and a sore throat may also occur early on. After two to four days, the disease can progress to the hemorrhagic phase, characterized by signs of bleeding. This may include bruising, nosebleeds (epistaxis), bleeding from the gums, blood in the urine (hematuria), and dark, tarry stools (melena). In severe cases, multi-organ failure can occur, leading to a fatality rate of 10% to 40%.
Diagnosis and Medical Care
Diagnosing CCHF involves laboratory tests to detect the virus or the body’s immune response. During the acute phase, molecular methods like Reverse Transcription Polymerase Chain Reaction (RT-PCR) and real-time PCR detect viral RNA. These methods are useful during the first week of illness.
Serological tests, such as Enzyme-Linked Immununsorbent Assay (ELISA), detect CCHFV-specific IgM and IgG antibodies, usually after the fifth day of the disease. While no broadly available specific antiviral treatment for CCHF is available, medical care focuses on supportive measures. This includes managing fluid and electrolyte balance, maintaining oxygenation, supporting blood pressure, and treating secondary infections. The antiviral drug Ribavirin has been used in some cases, with both oral and intravenous formulations, although its effectiveness can vary and studies have yielded mixed results.
Preventing Infection
Preventing CCHF involves addressing tick exposure, animal contact, and human-to-human transmission. In endemic areas, individuals should take protective measures against tick bites. This includes wearing long pants and sleeves, using tick repellents (e.g., DEET or permethrin) on exposed skin and clothing, and regularly checking for and removing ticks after outdoor activities.
Those who work with livestock or handle animal carcasses, especially in regions where the virus is present, should implement safe animal handling practices. This involves wearing gloves and other protective clothing when butchering or contacting animal blood or tissues. Since animals often do not show signs of infection, diligence is important.
In healthcare settings, strict infection control measures are important to prevent human-to-human spread. This includes standard precautions, isolating suspected CCHF patients, and ensuring proper sterilization of medical equipment and disposal of contaminated materials. Currently, no widely available human vaccine for CCHF exists, though research efforts are ongoing, and an inactivated virus vaccine is used in Bulgaria.
Where the Virus is Found
The Crimean-Congo Hemorrhagic Fever virus has a wide geographic distribution, making it one of the most widespread tick-borne viral diseases globally. It is considered endemic in various parts of Africa, the Balkans, the Middle East, and Asia, particularly in countries south of the 50th parallel north, aligning with the geographical limit and habitats of its principal tick vector, Hyalomma species.
Outbreaks of CCHF are often seasonal, typically coinciding with periods of increased tick activity and agricultural practices involving livestock. The movement of animals, which can carry infected ticks, also contributes to the spread of the virus to new areas. While the virus does not cause apparent disease in animals, they serve as important hosts for the ticks and can maintain the virus in the environment. This ecological interplay between ticks, animals, and environmental factors influences where and when human infections occur.