Drivers of Crimean-Congo Hemorrhagic Fever in Natural Host and Effects of Control Measures, Bulgaria

• Published in: Emerging Infectious Diseases
• Main Authors: Georgina Limon, Simona R. Tchakarova, Anna Ludi, Tsviatko Alexandrov, Iva Christova, Petya Petkova, Emmanuel Maze, Kelly Thomas, Natalie Baker, Marion England, Clare Browning, Ginette Wilsden, Sandra Belij-Rammerstorfer, Teresa Lambe, Anna Jolles, Miles Carroll, Roger Hewson, Simon Gubbins, Bryan Charleston, Nicholas A. Lyons
• Format: Article
• Language: English
• Published: Centers for Disease Control and Prevention 2025-09-01
• Subjects: Crimean-Congo hemorrhagic fever; Crimean-Congo hemorrhagic fever virus; CCHFV; vector-borne infections; viruses; zoonoses
• Online Access: https://wwwnc.cdc.gov/eid/article/31/9/24-1952_article
• ISSN: 1080-6040; 1080-6059

Crimean-Congo hemorrhagic fever (CCHF) is an emerging tickborne disease and a World Health Organization priority. Although humans are accidental hosts, infection can lead to hemorrhagic fever with a high fatality rate. Domestic animals play a critical role in disease transmission, but infected animals do not show clinical signs and viremia is short; thus, CCHF virus (CCHFV) infections can remain unobserved. During 2017–2019, we conducted 2 sequential observational studies followed by a multisite randomized controlled trial to determine spatial-temporal patterns and quantify drivers for CCHFV exposure in a natural host (sheep) in a CCHF-endemic area of Bulgaria. We found high-risk areas embedded in endemic regions. Animal characteristics were not correlated with seropositivity; however, a seasonality effect was observed, suggesting sampling time was a potential confounder. Force of infection varied across farms and over time. CCHFV transmission heterogeneity among farms is driven by preventive measures used to reduce exposure to ticks.