Abstract
Background
Tick-borne Encephalitis (TBE) is a CNS infection caused by the TBE virus (TBEV), transmitted by ticks or by ingestions of unpasteurized dairy products. Persisting sequelae occur in up to 50% of patients and case fatality rates are 0.4-6% (up to 20% in Russia). There is no specific treatment, but prevention exists. New areas of TBEV circulation were recently identified. Here the current distribution of the TBEV by the end of 2019 is summarized.
Methods
Data were obtained from solicitation of local expert data from countries in Europe and Asia on TBEV isolation, type of surveillance/reporting, past/current case counts, and vaccine uptake, supplemented by literature searches. Countries were classified as suggested by the European Centers for Disease Prevention and Control (ECDC) as TBE- “predisposed” (competent ticks present), “imperiled” (TBEV isolated), “affected” (sporadic autochthonous cases) or “endemic” (annually autochthonous cases).
Results
TBE has now been diagnosed in Eurasia from the United Kingdom, Norway and France in the west, northern Italy in the south, central/eastern Europe, Russia, China on to Japan in the east. “New endemic” countries in the last five years include the United Kingdom, the Netherlands, as well as “new endemic regions”, e.g. in France, Norway, Germany, Finland and Poland. Six countries are considered as predisposed only, three as imperiled, five as affected and 29 as endemic. Misclassification is likely as some countries have no testing (no test), incomplete testing and/or underreporting.
Conclusion
The main considerations of TBEV risk for oversea travelers to Eurasia are: 1) the exact region and terrain within a country; 2) the planned type of (outdoor) activity; 3) the reliability of within country TBEV surveillance. TBE incidences per region may fluctuate log-fold over just a few years and low reported case counts may reflect a lack of testing, and/or preventive measures including vaccine uptake, and underreporting. As the incidence of TBE is unpredictable, prevention measures should be considered for any person traveling or residing in a recognized TBE “risk area”.
Disclosures
Sarah Pugh, PhD, Pfizer (Employee, Shareholder) Wilhelm Erber, PhD, Pfizer (Employee, Shareholder) Andreas Pilz, PhD, Pfizer (Employee, Shareholder) Heinz-Josef Schmitt, MD, Pfizer (Employee, Shareholder)
Tick-Borne Encephalitis Virus in Ticks and Roe Deer, the Netherlands