Other - THL

Tick-borne encephalitis

In 2025, laboratories reported a total of 232 cases of tick-borne encephalitis to the National Infectious Diseases Register. In the previous year, 195 cases were reported, and in 2023 the number was 194. During the intensified monitoring period conducted by THL from 1 October 2024 to 30 September 2025, 228 cases of tick-borne encephalitis were identified. The highest number of cases occurred in July.

The increasing trend in tick-borne encephalitis infections is influenced by several factors. Increased awareness of the disease may partly contribute to the rise in reported cases. It has also been noted that environmental and climate changes affect the occurrence of tick-borne diseases.
During the most recent monitoring period, the age of those who became ill ranged from 4 to 84 years, with a mean age of 49 years (median 51 years). Of the cases, 26 were in persons under 18 years of age, including 4 preschool-aged children.

In Finland, the risk areas for tick-borne encephalitis are mainly located along the coast and near larger bodies of water.

Municipality-specific information on the occurrence of tick-borne encephalitis and vaccination recommendations can be found on the map available through the link below.
Map of tick-borne encephalitis occurrence and vaccination recommendations by locality (in Finnish)

Cases of tick‑borne encephalitis (TBE) in Finland by surveillance period
Year
2015	68
2016	61
2017	85
2018	79
2019	69
2020	91
2021	149
2022	126
2023	160
2024	201
2025	228

Enhanced monitoring of TBE occurrence

In Finland, the overall risk of contracting tick-borne encephalitis is generally low. The infection risk is higher particularly among people who spend time outdoors during the snow-free season in areas where the incidence of tick-borne encephalitis is high. In addition to the geographical area, the amount of time spent there also affects the risk.

THL monitors the number of cases through laboratory notifications submitted to the National Infectious Diseases Register. Findings of TBE virus antibodies are reported to the register. In addition, THL identifies likely exposure areas based on interviews with persons who have contracted the disease.