Crimean-Congo hemorrhagic fever (CCHF) is a viral hemorrhagic fever (VHF) syndrome that is caused by the Nairovirus genus of the Bunyaviridae viral family. Although first identified in the Crimea, this virus has been identified as the etiological agent of VHF in the Congo and worldwide.

This is a tick-borne illness carried by a variety of Ixodes (hard) ticks, although the primary vector is the Hyalomma tick, and the distribution of CCHF follows this tick worldwide. Domestic and wild animals, such as cattle, sheep, goats, and hares, serve as amplifying hosts for the illness. Hares and hedgehogs may be particularly important hosts, often infected by bites from immature ticks.

Transmission of this illness to humans generally occurs through bites from infected ticks and exposure to blood from infected animals. Ingestion of infected meats and milk can also cause infection. Human-to-human droplet transmission has been described, although infection generally occurs from exposure to blood through skin or mucous membranes. The incubation period is from 1-13 days, with shorter (1-3 days) periods following tick bites and up to 13 days following exposure to blood or tissues.

CCHF produces an initial prehemorrhagic phase illness with sudden onset of fever, weakness, malaise, and back pain lasting 2-7 days. Gastrointestinal symptoms of nausea, vomiting, abdominal pain, and bloody diarrhea are also common. Sharp mood changes, confusion, and aggression have also been described. The illness often does not progress beyond this phase.

The hemorrhagic phase usually develops suddenly, within 2-3 days of onset of illness. A petechial rash may develop first, followed by ecchymoses and then hematemesis, melena or hematochezia, epistaxis, hemoptysis, and bleeding from any venipuncture sites. Internal hemorrhages, particularly intracranial, may occur with progression to fulminant hepatitis with jaundice, DIC, hemorrhage, shock, and then death.

Asymptomatic illness is thought to be uncommon, but mild infections occur often, with the mortality rate of the hemorrhagic form reported to be 20%-50%.

Surviving patients generally begin recovery in 10-20 days after the onset of illness. Recovery is slow but generally complete.

At present, no vaccine is available.

CCHF is endemic to Eastern Europe and the Crimea, the Middle East, western China, Pakistan, and Africa. Occupations at higher risk for contracting CCHF include veterinarians, hunters, campers, hikers, and farmers.

Prevention is important and centers on avoiding tick bites and ingestion of infected foods (milk, meats). Tick repellants and barrier clothing are advised when traveling in endemic areas.