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Crimean-Congo Hemorrhagic Fever

What Is It, Causes, Spread, Signs, Symptoms, and More

Author: Georgina Tiarks

Editors: Alyssa Haag, Ian Mannarino, MD, Kelsey LaFayette, DNP, ARNP, FNP-C

Illustrator: Jessica Reynolds, MS

Copyeditor: Stacy M. Johnson, LMSW

What is Crimean-Congo hemorrhagic fever?

Crimean-Congo hemorrhagic fever (CCHF) is a viral, tick-borne hemorrhagic fever that can cause severe, life-threatening effects. The virus that causes CCHF, Orthonairovirus, is typically carried by Ixodes (hard) ticks, especially those in the genus Hyalomma. It can spread directly and indirectly to humans through animals, classifying it as a zoonotic disease. Livestock animals such as goats, cattle, sheep, camels, and hares are commonly susceptible. Orthonairovirus, named after Nairobi disease-causing hemorrhagic gastroenteritis in sheep, is responsible for causing numerous infectious diseases, including CCHF, Dugbe virus, Erve virus, and Tamdy virus. CCHF is highly notable due to its high lethality in humans, which makes it a global public health concern.  

When an infected tick bites an individual, the Orthonairovirus is transmitted to the affected person. Conversely, an animal can also become infected through tick bites and may infect a human if an individual comes in contact with the animal’s tissue or bodily fluids.

CCHF was originally named Crimean hemorrhagic fever after its discovery in Crimea in 1944. However, in 1969, there was a documented outbreak of CCHF in Belgian Congo, what is now known as the Democratic Republic of Congo. Shortly after, it was renamed Crimean-Congo hemorrhagic fever. Today, the disease can be found in various parts of the world with a wide distribution. The Centers for Disease Control and Prevention has recorded CCHF cases in the Mediterranean, Eastern Europe, Southern Europe, Middle East, Northwestern China, Central Asia, Africa, and India. It has also affected areas formerly known as the Soviet Union (e.g., Russian, Ukraine, Kazakhstan, and Turkmenistan).

What causes Crimean-Congo hemorrhagic fever?

Crimean-Congo hemorrhagic fever virus (CCHFV) is a part of the Orthonairovirus genus in the Nairoviridae family within the Bunyaviridae order. Like other Bunyaviruses, CCHFV is an enveloped (i.e., has an outer layer), negative-sense, single-stranded RNA virus (i.e., its genetic code is in its RNA form) with three segments. The segments are composed of a nucleocapsid protein, glycoproteins, and a polypeptide protein.

Ticks are both a reservoir and vector for the CCHFV. A reservoir is the virus’ natural habitat where it can complete its life cycle and multiply. Alternatively, a vector is responsible for the transmission of the virus. The virus has been found in Ixodidae ticks, also considered hard ticks; however, they are most commonly found in the Hyalomma tick genus. 

How is Crimean-Congo hemorrhagic fever spread?

CCHF can be spread via both ticks and bodily fluids. Ticks from the Hyalomma genus are responsible for transmitting the Orthonairovirus to humans and animals. Sheep, cattle, and goats are particularly susceptible to infection via ticks. Small mammals and birds may also be carriers. Handlers are at risk of contracting infected blood and tissue from infected animals. 

In addition to animal-to-human contact, CCHF may be spread human-to-human. Once a person has become infected, they can transmit the virus to others through bodily fluids, such as blood. There are also known cases of CCHF spread through hospitals due to poor sanitation and improper sterilization methods.  

The spread of CCHF can be prevented through a multitude of practices. Farm workers in endemic areas can use DEET (i.e., N, N-diethyl-m-toluamide), an effective insect repellent, to prevent tick bites. They may also be encouraged to wear protective clothing, such as long sleeves, pants, and boots. Avoiding contact with bodily fluids may also be recommended for those working closely amongst animals on farms or slaughterhouses. Healthcare workers should also be cautioned to wear personal protective equipment, like gloves, masks, and eyewear, when working with infected tissue and blood products. 

What are the signs and symptoms of Crimean-Congo hemorrhagic fever?

The signs and symptoms of Crimean-Congo hemorrhagic fever arise acutely and progressively worsen. Within the first few days after coming in contact with the virus, symptoms include headache, high fever, vomiting, abdominal pain, joint pain, and back pain. Red eyes, jaundice (i.e., yellowing of the skin), or flushing of the skin may follow. Soon after, signs of hemorrhage (i.e., internal bleeding), such as petechiae (i.e., 1 mm round red spots) of the skin, may arise.  Severe bleeding may occur days later, such as ecchymoses (i.e., bruising), nosebleeds, and bleeding from open wound sites. Previous cases indicate a fatality rate that varies between 9-50%.

How is Crimean-Congo hemorrhagic fever diagnosed?

A health care professional must examine an individual to diagnose Crimean-Congo hemorrhagic fever. They can determine whether additional testing measures are warranted based on the individual’s medical history and symptoms. Blood tests may be necessary to detect the virus's viral antigens, antibodies, or viral RNA. An ELISA (i.e., enzyme-linked immunosorbent assay) is a unique laboratory test that can detect antibodies against CCHFV or the viral antigen in an individual’s blood. An RT-PCR (i.e., reverse transcriptase polymerase chain reaction) may also be used to detect viral RNA.

Baseline lab work includes complete blood count (CBC) and comprehensive metabolic panel (CMP). A CBC can determine whether lymphocytes (i.e., a type of immune cells) are elevated, thereby indicating an infection. Meanwhile, a CMP can establish whether electrolyte abnormalities, kidney problems or liver damage are present.

How is Crimean-Congo hemorrhagic fever treated?

There is currently no cure for CCHF; Crimean-Congo hemorrhagic fever may be managed through supportive care. Currently, there are also no definitive treatments or vaccines to combat CCHF. Supportive care may include the replacement of fluids and electrolytes, oxygenation or ventilatory support, and pain medication (e.g., acetaminophen), among others. Depending on their hemodynamic stability, they may also require blood pressure support or blood products, including erythrocytes (i.e., red blood cells), platelets (i.e., cells involved in blood clotting), or fresh frozen plasma (i.e., a portion of donated blood products). Some studies have also shown that ribavirin, an antiviral drug, is effective in treating individuals with Crimean-Congo hemorrhagic fever. Therefore, the World Health Organization (WHO) recommends distributing ribavirin to anyone infected. Although the virus is often fatal, in the situations where an individual survives, their recovery is typically slow.

When cases of CCHF are discovered, they are advised to be reported to the international community, such as the World Health Organization, so that measures may be put into place to prevent further spread. CCHF is a Biosafety Level 4 pathogen, meaning healthcare workers must follow strict procedures. Healthcare workers must wear a positive pressure suit and pass through chemical showers when leaving infected areas. Airflow is also regulated and contained. Individuals infected should be isolated in isolation rooms with biocontainment procedures to prevent nosocomial (i.e., originating in a hospital) spread. For those at significant risks, such as healthcare workers, ribavirin may be administered prophylactically. 

What are the essential facts to know about Crimean-Congo hemorrhagic fever?

Crimean-Congo hemorrhagic fever is a viral infectious disease. It is a type of hemorrhagic fever transmitted via tick bites or contact with infected bodily fluids. Crimean-Congo hemorrhagic fever virus is a subtype of the Orthonairovirus genus. It is a part of the Nairoviridae family and Bunyaviridae order. It was initially discovered in Crimea, resulting in the initial naming of Crimean hemorrhagic fever. However, when it was later found in Congo, it was renamed Crimean-Congo hemorrhagic fever. It has been found in several countries worldwide, including Eastern Europe, the Mediterranean, China, Africa, and India.

Ticks carry the virus and can infect humans when bitten. Animals may also contract the virus through tick bites, and humans may be indirectly infected when they contact with infected animal fluids. During the first few days after infection, an individual may experience headache, high fever, nausea, and other constitutional symptoms (i.e., symptoms affecting different body parts). As the disease progresses, signs of hemorrhage such as nosebleeds, petechiae, and ecchymoses can result in lethal bleeding. Diagnosis occurs through blood work testing for viral particles or antibodies to the virus. Treatment is primarily via supportive therapy, including fluid replacement, blood pressure, and ventilatory support. Some studies have also claimed that ribavirin can prove beneficial.

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