Crimean-Congo hemorrhagic fever (CCHF) is caused by a zoonotic virus that seems to be carried asymptomatically in animals but can be a serious threat to humans. This disease typically begins as a nonspecific flu-like illness, but some cases progress to a severe, life-threatening hemorrhagic syndrome. Intensive supportive care is required in serious cases, and the value of antiviral agents such as ribavirin is still unclear.
Crimean-Congo hemorrhagic fever virus (CCHFV) is widely distributed in the Eastern Hemisphere. However, it can circulate for years without being recognized, as subclinical infections and mild cases seem to be relatively common, and sporadic severe cases can be misdiagnosed as hemorrhagic illnesses caused by other organisms. In recent years, the presence of CCHFV has been recognized in a number of countries for the first time.
Crimean-Congo hemorrhagic fever is caused by Crimean-Congo hemorrhagic fever virus (CCHFV), a member of the genus Orthonairovirus in the family Nairoviridae and order Bunyavirales. CCHFV belongs to the CCHF serogroup, which also includes viruses such as Tofla virus and Hazara virus. Six or seven major genetic clades of CCHFV have been recognized. Some strains, such as the AP92 strain in Greece and related viruses in Turkey, might be less virulent than others.
A wide variety of domestic and wild vertebrates, including birds, may experience subclinical infection. Host preference of ticks carrying CCHF vary by life stage, with larvae and nymphs preferring small mammals and ground birds whereas adults may more likely be found on large mammals, such as livestock.
Reservoirs of CCHF include various domestic and wild animals. Common examples include livestock (cattle, sheep, and goats), hares, hedgehogs, and other small vertebrates. CCHFV remains in livestock for up to a week. All animals appear to show no clinical signs.
CCHF is transmitted to people through:
• Bites from infected ticks
• Direct, unprotected contact with infected animals including during slaughter of animals with ticks attached
• Direct physical contact with body fluids of a person suffering from CCHF
• Direct contact with a body of a person who has died of CCHF
A person with CCHF can have the following signs and symptoms
• Sudden on-set of high fever
• Back pain
• Joint pain
• Abdominal pain
• Dizziness (feeling that you are losing your balance and about to fall)
• Neck pain and stiffness
• The person who has been in contact with a person who has similar symptoms or animals infested with ticks, or has had a tick bite. In addition, the person can also have any of the following:
• Sore throat
• Sharp mood swings
• Bleeding, bruising or a rash After 2 or 4 days, the patient may experience sleeplessness and depression
Symptoms are non-specific; clinical diagnosis may be difficult. Differential diagnosis includes other viral haemorrhagic fevers, malaria, typhoid fever, shigellosis, and other viral and bacterial diseases.
Patient history is essential and should include:
• Exposure to ticks;
• Or exposure to wild animals and livestock;
• And/or area/village endemic for CCHF;
• And/or contact with CCHF cases.
Definitive diagnosis requires testing:
• Reverse transcriptase polymerase chain reaction (RT-PCR) assay;
• IgG and IgM antibodies enzyme-linked immunosorbent assay (ELISA);
• Antigen detection tests;
• Virus isolation by cell culture.
Treatment is mainly supportive. Seriously ill patients require intensive care. Ribavirin has been widely used to help treat Crimean-Congo hemorrhagic fever, but its efficacy has not been conclusively demonstrated and is questioned by some authors.
This drug appears to be most effective when it is given very soon after the onset of clinical signs (e.g., during the first 48 hours). There is little information about anti-CCHFV hyperimmune serum, although it is reported to be administered routinely to patients in Bulgaria. Favipiravir, alone or in combination with ribavirin, appears to be promising in animal models but had not been tested in humans.
Protect yourself from tick bites
1. Avoid tick-infested areas.
2. Wear light colored clothing for easy finding of ticks on clothes.
3. Wear protective clothing (long sleeves, long pants).
4. Tuck your pant legs into your socks so that ticks cannot crawl up inside of your pant legs.
5. Use chemical repellent with DEET (on skin) and acaricides (tick killer) on boots and clothing. Perform daily tick checks: regularly examine clothes and skin in search of ticks and remove them.