Crimean-Congo hemorrhagic fever

Crimean-Congo hemorrhagic fever is a viral hemorrhagic fever caused by the Crimean-Congo hemorrhagic fever virus, a tick-borne Nairovirus within the Bunyaviridae family ^[1][2][3]. It is maintained in nature through tick-vertebrate cycles and is the most important tick-borne viral disease of humans by geographic reach ^[1][4].

After a tick bite, illness begins after an incubation of 1–3 days (up to 9 days), while contact with infected tissues yields onset in about 5–6 days (up to 13 days) ^[2]. Symptom onset is abrupt and may include fever, muscle ache, dizziness, neck and back pain, headache, sore eyes, and photophobia, later with nausea, vomiting, diarrhea, abdominal pain, sore throat, mood swings, and confusion ^[2]. Within days, agitation may give way to sleepiness and depression, with localized upper-right abdominal pain and detectable liver enlargement, alongside tachycardia and lymphadenopathy ^[2].

CCHF is endemic in Africa, the Balkans, the Middle East, and Asia south of the 50th parallel north, causing sporadic cases and outbreaks across a vast area from western China to southeastern Europe and throughout most of Africa ^[1][2][4]. Global meta-analysis indicates mean seroprevalence of 4.7% in humans and 24.6% in animals, with livestock rates of 17.1–29.3% depending on species, and at-risk professionals showing 7.5-fold higher seroprevalence than the general population ^[5]. Reported case fatality ranges from 10–40% to 30% or higher, and the disease is described as the most widespread tick-borne viral disease affecting humans ^[1][2][5][3].

The virus is transmitted to humans principally by bites of infected Hyalomma ticks, and additionally through contact with blood or tissues of infected animals during or just after slaughter ^[1][2][4]. Human-to-human spread occurs via close contact with body fluids of infected persons, including hospital-acquired infection through contaminated equipment or needles ^[1]. Vertical and horizontal maintenance cycles involve ixodid ticks and wild or domestic vertebrates that show no apparent illness ^[4].

Controlling infection in animals and ticks is challenging because the tick-animal cycle is usually unnoticed and domestic animal infection is typically silent; tick control with acaricides is realistic mainly for well-managed livestock facilities, such as quarantining ostriches to remain tick-free for 14 days after an abattoir outbreak ^[1]. WHO supports surveillance, diagnostics, and outbreak response and provides standard-precaution guidance to reduce bloodborne pathogen transmission in care settings ^[1]. No licensed vaccines or specific antivirals are available, underscoring the reliance on vector and exposure control ^[3].

1. 1 World Health Organization. Crimean-Congo haemorrhagic fever [Internet]. cited 20 May 2026. Available from: https://www.who.int/news-room/fact-sheets/detail/crimean-congo-haemorrhagic-fever
2. 2 World Health Organization. Crimean-Congo haemorrhagic fever [Internet]. cited 20 May 2026. Available from: https://www.who.int/health-topics/crimean-congo-haemorrhagic-fever
3. 3 Hawman DW et al. Crimean-Congo haemorrhagic fever virus. Nat Rev Microbiol. 2023 Jul. PMID: 36918725. doi: 10.1038/s41579-023-00871-9. PubMed: https://pubmed.ncbi.nlm.nih.gov/36918725/
4. 4 Bente DA et al. Crimean-Congo hemorrhagic fever: history, epidemiology, pathogenesis, clinical syndrome and genetic diversity. Antiviral Res. 2013 Oct. PMID: 23906741. doi: 10.1016/j.antiviral.2013.07.006. PubMed: https://pubmed.ncbi.nlm.nih.gov/23906741/
5. 5 Nasirian H et al. Crimean-Congo hemorrhagic fever (CCHF) seroprevalence: A systematic review and meta-analysis. Acta Trop. 2019 Aug. PMID: 31108083. doi: 10.1016/j.actatropica.2019.05.019. PubMed: https://pubmed.ncbi.nlm.nih.gov/31108083/