Tick-borne encephalitis more common: number of hospitalized patients increased

Last year, the total number of TBE cases diagnosed in Finland was 195, but by the end of November 2025, 227 cases have already been entered in the Finnish National Infectious Diseases Register.

In the HUS region, the number of TBE cases has increased from 91 in 2024 to 120 at the end of November 2025.  TBE has been common in Western Uusimaa previously as well, but now the number of cases has increased in Helsinki especially. Some of the affected Helsinki residents may have contracted the infection elsewhere. All cases of TBE are annually reported to the National Infectious Diseases Register maintained by the Finnish Institute for Health and Welfare (THL).

Three out of four patients have incomplete vaccinations

The increase in the number of cases has been evident in the West Uusimaa wellbeing services county, and at HUS emergency departments in Lohja, Jorvi, and Meilahti hospitals. At worst, during the summer, a third of the patients admitted to Jorvi Hospital Neurology Ward had TBE. In the HUS region, 14% of TBE patients needed intensive or intermediate care. Some of the patients who received intensive care require long rehabilitation before they can be discharged.

Two percent of patients diagnosed with TBE died. The actual mortality is lower than this, as a significant number of minor TBE cases are never diagnosed. Of all patients with TBE, 69% had no vaccination, and 13% had received incomplete immunization or the immunization was no longer effective.

TBE more common than herpes

TBE has surpassed herpesvirus as a leading cause of severe encephalitis, at least during the summer. Herpesviruses remain a significant cause of encephalitis and are treated with antiviral medication. The occurrence of herpesviruses does not change with the seasons, whereas TBE occurs mainly in the summer and early fall.

The TBE virus is transmitted through tick bites already at an early stage of the bite. Only some of the infected have symptoms, and about 20–30% of those with symptoms develop actual encephalitis.

Get TBE vaccine now

There is a vaccination against TBE, and it prevents infections in about 90% of vaccinated people. The vaccine is free for people who live in certain risk areas.

“People who spend time in nature in the risk areas should now get the TBE vaccine for next summer. This could decrease the amount of TBE cases,” says Infectious Diseases Specialist Elisa Kortela from HUS Inflammation Center.

The immunization is complete after a series of three doses. Everyone will also need a booster three years later, after which the interval of boosters depends on the person's age.

The majority of tick bites remain unnoticed. When roaming in nature, check if the region is one of the tick-bite risk regions defined by THL, where the vaccines are especially recommended. These include Lohja, Kirkkonummi, Espoo, Sipoo, and parts of Helsinki. Ticks may also end up indoors in pets’ fur.