Tick-borne encephalitis

Tick-borne encephalitis is the clinical disease caused by tick-borne encephalitis virus (TBEV), which is identified in the sources as a flavivirus and an arboviral etiologic agent ^[1][2]. The condition is framed as a tick-borne viral disease of major relevance in Europe and Asia, with reported increases in incidence and geographical range in recent years ^[1][2]. The provided sources do not add further source-backed detail on viral subtype distribution beyond noting that mortality depends on subtype ^[2].

Human TBEV infection may be asymptomatic, or it may present with symptoms ranging from mild influenza-like illness to severe neurological disease ^[1][2]. One review describes a characteristic biphasic course, beginning after a short incubation period with a viraemic phase marked by non-specific flu-like symptoms, followed after an asymptomatic interval of 2–7 days by a neurological phase in more than half of patients ^[2]. Neurological involvement is usually central and more rarely peripheral, and the sources note that after acute disease a minority of patients have long-term neurological deficits ^[2]. A post-encephalitic syndrome is reported in 40%–50% of patients and is said to impair daily activities and quality of life ^[2]. Mortality is described as low, around 1% of confirmed cases, depending on viral subtype ^[2].

TBEV is reported as commonly found in at least 27 countries across Europe and Asia, and it is described as one of the most important tick-borne viral diseases in these regions ^[1][2]. The disease is characterized as emerging, with steadily increasing case numbers over recent decades and a rising incidence in more than half of the European countries analyzed in recent studies ^[1][2]. The sources estimate 10,000 to 15,000 patients annually and state that cases in Europe are reported every year ^[2][1]. In nature, ticks and small mammals are said to help maintain the virus, and the virus can also infect dogs, horses, cattle, and small ruminants ^[1].

Humans are described as incidental hosts, with infection occurring primarily through the bite of an infected tick ^[1][2]. Less common transmission is reported through the alimentary route after consumption of unpasteurized milk or milk products from infected animals, and one review also mentions aerosols as a much less common route ^[1][2]. The sources further note transmission between ticks, animals, and humans, with ticks and small mammals contributing to maintenance in nature ^[1].

The supplied sources do not identify specific human demographic risk groups by age, sex, occupation, or travel status ^[1][2]. They do indicate that humans are incidental hosts and that exposure occurs through infected tick bites or, less commonly, contaminated milk or milk products, so persons with such exposures are the main source-backed risk context ^[1][2]. The virus is also reported to affect dogs, horses, cattle, and small ruminants, although the sources do not provide further detail on comparative risk or disease patterns in these animals ^[1].

The sources identify immunization and protection against tick bites as critical measures for preventing tick-borne encephalitis ^[1]. They also imply exposure control through avoidance of unpasteurized milk or milk products from infected animals, given the alimentary route of transmission ^[1][2]. No further source-backed detail on vaccine schedules, specific repellents, or other prevention protocols is available in the supplied material ^[1][2].

In surveillance terms, tick-borne encephalitis should be read as an expanding tick-borne arboviral infection with persistent annual case reporting in Europe and documented growth in incidence and geographic range ^[1][2]. Because many infections may be asymptomatic and clinical illness may progress from a nonspecific febrile phase to neurological disease, case ascertainment may depend on recognizing the biphasic pattern when present ^[2]. The supplied sources do not provide standardized case-definition details, but they do support attention to both tick exposure and milk-borne exposure in monitoring investigations ^[1][2].

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 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/
3. 3 Gundamraj V et al. Viral meningitis and encephalitis: an update. Curr Opin Infect Dis. 2023 Jun 1. PMID: 37093042. doi: 10.1097/QCO.0000000000000922. PubMed: https://pubmed.ncbi.nlm.nih.gov/37093042/
4. 4 Tick-borne encephalitis. Revue Scientifique et Technique de l'OIE. 2015. doi: 10.20506/rst.34.2.2371. DOI: https://doi.org/10.20506/rst.34.2.2371
5. 5 Tick-Borne Encephalitis. Encyclopedic Reference of Parasitology. None. doi: 10.1007/3-540-29835-5_2494. DOI: https://doi.org/10.1007/3-540-29835-5_2494
6. 6 Tick-Borne Encephalitis. Tick-Borne Diseases of Humans. 2014. doi: 10.1128/9781555816490.ch9. DOI: https://doi.org/10.1128/9781555816490.ch9

ICD-10

A84

ICD-11

1D49

Total cases

4K

Peak month

2025-06

Coverage

2 reporting countries · 2013-01-01 → 2026-06-01