Wijburg et al.
Targeted monitoring informed by mapping the ongoing spread of tick-borne encephalitis virus in the Netherlands. Euro Surveill. 2026;31:2500767. doi:10.2807/1560-7917.ES.2026.31.2500767
In the Netherlands, tick-borne encephalitis (TBE) virus was first detected in 2015, and in 2025, TBE became a notifiable disease. However, uncertainties remain regarding the geographical distribution of the virus and the mechanisms by which it is maintained within ecosystems. This study aimed to address these knowledge gaps by identifying TBE risk areas through habitat suitability mapping. Specifically, areas were classified according to their suitability for sustained TBE virus transmission based on the presence of competent small rodent hosts, medium- to large-sized mammals, birds, and lizards.
The analyses also included serological detection of antibodies in wildlife and the use of maps of confirmed TBE microfoci. In addition, data from the national land use database were incorporated to identify habitats suitable or unsuitable for ticks. Tick sampling was conducted in areas where antibody-positive roe deer and human TBE cases had been identified, and collected ticks were tested for the presence of TBE virus.
In summary, several areas with high TBE virus habitat suitability and relatively high recreational activity were identified. Screening of TBE-positive roe deer sera revealed six new regions with evidence of TBE virus circulation. Among 4,787 questing ticks analyzed, 0.4% tested positive for TBE virus in a newly identified TBE area in Zeeland.
The findings demonstrate that the geographical range of TBE virus continues to expand within the Netherlands, with evidence of emergence in ticks and wildlife in previously unaffected regions. The virus may not yet have fully occupied all suitable ecological niches. Certain mammalian hosts, such as roe deer and bank voles, are increasing in abundance, whereas some bird populations are declining. These ecological changes are likely to influence tick-host interactions and the transmission dynamics of TBE virus.
The habitat suitability maps developed in this study may provide a basis for risk-based surveillance and targeted control strategies. They also offer a valuable tool to strengthen preparedness for TBE, including in regions where the virus has not yet been detected.