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Identifying hotspots and risk factors for tick-borne encephalitis virus emergence at its range margins to guide interventions, Great Britain
- Richard MJ Hassall1 , Maya Holding2,3 , Jolyon M Medlock4 , Festus A Asaaga1 , Sophie O Vanwambeke5 , Roger Hewson2,6 , Bethan V Purse1
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View Affiliations Hide AffiliationsAffiliations: 1 UK Centre for Ecology and Hydrology, Benson Lane, Crowmarsh Gifford, Wallingford, United Kingdom 2 Virology and Pathogenesis Group, Specialist Microbiology and Laboratories, UK Health Security Agency, Porton Down, Salisbury, United Kingdom 3 National Institute for Health and Care Research (NIHR) Health Protection Research Unit in Emerging and Zoonotic Infections at the University of Liverpool, Liverpool, United Kingdom 4 Medical Entomology and Zoonoses Ecology, Climate Change and Health Security, UK Health Security Agency, Porton Down, Salisbury, United Kingdom 5 Université catholique de Louvain (UCLouvain), Earth & Life Institute, Earth and Climate Research Center, Louvain-la-Neuve, Belgium 6 Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United KingdomRichard Hassallricsal ceh.ac.uk
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Citation style for this article: Hassall Richard MJ, Holding Maya, Medlock Jolyon M, Asaaga Festus A, Vanwambeke Sophie O, Hewson Roger, Purse Bethan V. Identifying hotspots and risk factors for tick-borne encephalitis virus emergence at its range margins to guide interventions, Great Britain. Euro Surveill. 2025;30(13):pii=2400441. https://doi.org/10.2807/1560-7917.ES.2025.30.13.2400441 Received: 05 Jul 2024; Accepted: 12 Nov 2024
Abstract
Tick-borne encephalitis virus (TBEV) is expanding its range in Europe, with increasing human cases reported. Since the first detection of TBEV in ticks in the United Kingdom in 2019, one possible, two probable and two confirmed autochthonous cases in humans have been reported.
We aimed to understand the environmental and ecological factors limiting TBEV foci at their range edge and predict suitable areas for TBEV establishment across Great Britain (GB) by modelling patterns of exposure to TBEV in deer.
We developed spatial risk models for TBEV by integrating data between 2018 and 2021 on antibodies against tick-borne flavivirus in fallow, muntjac, red and roe deer with data on potential risk factors, including climate, land use, forest connectivity and distributions of bank voles and yellow-necked mice. We overlayed modelled suitability for TBEV exposure across GB with estimations on number of visitors to predict areas of high human exposure risk.
Models for fallow, muntjac and roe deer performed well in independent validation (Boyce index > 0.92). Probable exposure to TBEV was more likely to occur in sites with a greater percentage cover of coniferous woodland, with multiple deer species, higher winter temperatures and rates of spring warming.
The resulting TBEV suitability maps can be used by public health bodies in GB to tailor surveillance and identify probable high-risk areas for human exposure to guide awareness raising and vaccination policy. Combining animal surveillance and iterative spatial risk modelling can enhance preparedness in areas of tick-borne disease emergence.

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