Crimean-Congo Hemorrhagic Fever

Crimean-Congo Hemorrhagic Fever (CCHF) is an acute viral zoonotic infection transmitted by ticks, characterized clinically by fever and hemorrhage. The causative agent is the Crimean-Congo Hemorrhagic Fever Virus (CCHFV), a single-stranded RNA virus belonging to the Nairovirus genus of the Bunyaviridae family. Infection typically begins with prodromal symptoms such as fever, malaise, anorexia, muscle and headache pain, and in severe cases can lead to widespread hemorrhage throughout the body. CCHF is a potentially fatal disease with significant public health consequences.

The history of the disease extends back to the 12th century. In the modern era, it was first identified in the Crimea region of the Soviet Union during 1944–1945. Similar cases were observed in Congo in 1956, leading to the naming of the virus. In 1969, it was established that the agents responsible in Crimea and Congo were the same virus. The first confirmed cases in Türkiye were reported in 2003.

Causative Agent and Vector

The causative agent, Crimean-Congo Hemorrhagic Fever Virus (CCHFV), is an enveloped virus with negative-sense RNA. In nature, the virus is primarily transmitted by ticks. In Türkiye, the main vector species is Hyalomma marginatum. These ticks can directly transmit the virus to animals and humans, and also transmit it between generations through transovarial (via eggs) and transstadial (between life stages) pathways.

Transmission Routes

Tick Bites

The primary mode of transmission is through the bite of infected ticks. Ticks acquire the virus by feeding on the blood of infected animals and subsequently transmit it to humans. Tick attachment is often not noticeable to the naked eye.

Animal and Animal Product Exposure

Human infection can also occur through direct contact with the blood, tissues, or other bodily fluids of infected animals during the viremic phase. Animals typically exhibit asymptomatic infection, which complicates disease control efforts.

Human-to-Human Transmission

Human-to-human transmission occurs through unprotected contact with the blood, bodily fluids, feces, or respiratory secretions of infected individuals. This route poses a particular risk to healthcare workers. Laboratory exposure is also included in this category.

Clinical Course and Symptoms

The incubation period is generally 1–3 days (up to 9 days) after a tick bite, and 5–6 days (up to 13 days) after exposure to infected material.

The disease begins with symptoms such as high fever, muscle and headache pain, malaise, anorexia, nausea, vomiting, and diarrhea. In some cases, findings such as petechiae, ecchymoses, bleeding from the nose, gums, and gastrointestinal tract may be observed. In advanced stages, liver dysfunction, disseminated intravascular coagulation (DIC), and multiorgan failure may develop.

Epidemiology

CCHF was first identified in Türkiye in 2002 in Tokat and surrounding areas, with confirmed cases documented in 2003. The infection is most prevalent in the interior regions of the Central and Eastern Black Sea, as well as the northern parts of Central Anatolia and Eastern Anatolia.

Case numbers typically increase during spring and summer months, coinciding with heightened tick biological activity. The annual incidence in Türkiye varies, with the highest number of cases—1,318—recorded in 2009. The case fatality rate is approximately 4–5%.

Diagnosis

Diagnosis is established through clinical findings combined with serological tests (detection of IgM and IgG antibodies by ELISA), RT-PCR, and virus isolation. Early diagnosis can positively influence disease outcome.

Prevention and Control

The most effective method for preventing the spread of the disease is personal protection. In tick-risk areas, wearing protective clothing that covers the body, choosing light-colored garments, and promptly detecting and removing attached ticks are essential. When removing ticks, bare-handed contact must be avoided; appropriate tools should be used.

When handling animals, protective equipment such as gloves must be used, and particular caution is required during animal slaughter and care. Healthcare workers must use personal protective equipment including gloves, masks, and gowns when in contact with CCHF patients.

In Türkiye, education, awareness-raising, and public information campaigns to control the disease are led by the Ministry of Health. An effective, proven vaccine is not yet available, but vaccine development efforts are ongoing in the country.

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