Tick-borne encephalitis: An ancient pathology, but a current emergence in Europe

Tick-borne encephalitis (TBE), which is caused by the tick-borne encephalitis virus (TBEV), is primarily transmitted to humans through Ixodes bites of infected ticks of the genus Ixodes and, more rarely, by the consumption of contaminated dairy products. TBEV encompasses three main subtypes with distinct degrees of severity and clinical courses: European (TBEV-Eu), Siberian (TBEV-Sib), and Far Eastern (TBEV-FE). Over the past decade, TBE epidemiology has significantly changed in Europe, with increasing incidence in endemic countries and the discovery of new human case foci and areas of virus circulation. This emergence involves many factors of which the impacts are not easily determined. While most TBEV-Eu infections are asymptomatic, some patients develop signs of central nervous system involvement that can be severe (meningitis, encephalitis). While the mortality rate in humans is low (<2 %), post-infectious sequelae (cognitive and/or motor) can occur in up to 40 % of cases. While TBE treatment is symptomatic, several antiviral treatments are under study. The emergence of TBEV in Europe, particularly in France, represents a significant public health issue. This review provides an up-to-date overview of the latest data concerning TBE, focusing on the epidemiology and clinical, diagnostic, and therapeutic aspects of this emerging infection.