Assessing the risks of tick-borne encephalitis virus transmission through substances of human origin

TBE is a viral disease transmitted primarily through tick bites. Between 2013 and 2022, 28 680 confirmed TBE cases were reported in the EU/EEA, with the majority occurring in central and northern Europe. The majority of TBE virus infections remain asymptomatic. However, long-term conditions have been reported in a substantial proportion of patients with neurological symptoms, and a case-fatality rate of around 0.5% is generally reported.

While TBE virus transmission through SoHO is documented, the assessment suggests such occurrences are exceedingly rare. Notably, two cases were reported via blood transfusion from a single donor and three through organ transplantation, also from a single donor. While the risk of TBE virus transmission through blood transfusion cannot be assessed, the likelihood of TBE virus transmission through blood transfusion leading to symptomatic disease is considered very low. The risk of TBE virus transmission through organ transplantation is considered low. In the absence of reported cases, the risk of TBE virus transmission through tissue and cell transplantation cannot be assessed.

ECDC emphasises that while preventive measures can be considered during TBE virus transmission periods, uncertainties remain due to considerable research gaps. Recommendations include deferring blood donors who report recent tick bites for 28 days and conducting serological and molecular tests for TBE virus in organ, tissue, and cell donors who may have been exposed. Additionally, enhancing vaccination rates in highly endemic areas could bolster overall safety concerning TBE virus transmission through SoHO.

The report acknowledges several uncertainties related to TBE virus infection through SoHO, as such, continued research and vigilance are necessary to safeguard public health.