Tick-borne encephalitis

Tick-borne encephalitis is a viral disease of the central nervous system caused by tick-borne encephalitis virus, a member of the Flaviviridae family, and is considered among the most important tick-borne viral illnesses in Europe and Asia ^[1][2][3]. The agent is a positive-sense single-stranded RNA flavivirus found in at least 27 European and Asian countries ^[2][3].

Many TBEV infections are asymptomatic, but clinical illness can range from mild influenza-like signs to severe neurological disease ^[1][2]. After a 2–28 day incubation, an initial phase of fever, headache, fatigue, and malaise may occur, followed by an asymptomatic interval and then, in a subset of patients, a second phase with meningitis, encephalitis, myelitis, or radiculitis and fever exceeding 40 °C ^[2][3]. Fatality is low at about 1% of confirmed cases, though some survivors experience long-term deficits or post-encephalitic syndrome ^[2][3].

Tick-borne encephalitis (TBE), caused by the tick-borne encephalitis virus (TBEV), is considered one of the most important tick-borne viral diseases in Europe and Asia ^[1]. In recent years, an increase in the incidence of TBE as well as an expanding geographical range of the disease have been observed ^[1]. Despite the COVID-19 pandemic and associated restrictions, TBE incidence is rising in more than half of the European countries analyzed in recent studies, with cases reported annually in Europe ^[1]. In France, TBE is much less common than Lyme borreliosis, with approximately 20 cases per year ^[4].

The virus circulates among ticks, small mammals, and humans, with ticks and small mammals maintaining TBEV in nature ^[1]. Humans are usually infected through the bite of an infected tick, and rarely via consumption of unpasteurized milk from infected animals or through aerosols, with no direct person-to-person spread ^[1][2][3]. Exposure commonly occurs during outdoor activity in forested areas up to about 2000 meters elevation ^[2].

No specific treatment exists for TBE, so prevention relies on immunization and avoidance of tick bites ^[1]. Mechanical protection through body-covering clothing and chemical repellents reduce tick contact, while early tick detection and proper removal lower infection risk after exposure ^[1][4]. In settings such as France, no human vaccine is licensed and prophylactic antibiotics are not recommended, leaving behavioral and tick-bite measures as the primary defense ^[4].

1. 1 Kwasnik M et al. Tick-Borne Encephalitis-Review of the Current Status. J Clin Med. 2023 Oct 18. PMID: 37892741. doi: 10.3390/jcm12206603. PubMed: https://pubmed.ncbi.nlm.nih.gov/37892741/
2. 2 World Health Organization. Tick-borne encephalitis [Internet]. cited 23 Oct 2026. Available from: https://www.who.int/health-topics/tick-borne-encephalitis
3. 3 Chiffi G et al. Tick-borne encephalitis: A comprehensive review of the epidemiology, virology, and clinical picture. Rev Med Virol. 2023 Sep. PMID: 37392370. doi: 10.1002/rmv.2470. PubMed: https://pubmed.ncbi.nlm.nih.gov/37392370/
4. 4 Figoni J et al. Lyme borreliosis and other tick-borne diseases. Guidelines from the French Scientific Societies (I): prevention, epidemiology, diagnosis. Med Mal Infect. 2019 Aug. PMID: 31097370. doi: 10.1016/j.medmal.2019.04.381. PubMed: https://pubmed.ncbi.nlm.nih.gov/31097370/