Tick-borne encephalitis in Finland

Tick-borne encephalitis (TBE) is a viral disease transmitted through the bite of ticks. The TBE virus, which belongs to the flavivirus family, can cause encephalitis, or inflammation of the brain, at its worst.

Tick-borne encephalitis occurs in a wide area from Central Europe through Siberia to Japan. There are three different subtypes of the TBE virus: European, Siberian and Far Eastern type. In Finland, the most common type is the European type, but the Siberian type has also been found.

In Finland, the disease occurs mainly in coastal regions but also in the border counties of southeastern Finland. In Finland, an average of 1–2% of ticks in risk areas carry tick-borne encephalitis.

The Finnish Institute for Health and Welfare’s (THL) assessment of new tick-borne encephalitis cases is conducted over the course of a year, from the beginning of October to the end of September of the following year.

Between October 1, 2023 and September 30, 2024, 200 new cases of tick-borne encephalitis were reported to the Finnish Institute for Health and Welfare's infectious disease register.

Symptoms of tick-borne encephalitis occur in 10–30% of those infected. The time from the bite to the first symptoms can vary between 4–28 days.

Tick-borne encephalitis typically has a two-stage clinical picture :

About a week after the bite, the first stage appears, with symptoms including fever, a vague feeling of malaise and a feeling of illness. This stage lasts on average less than 7 days (usually around 4-7 days). The majority of symptoms end here.

After an asymptomatic phase of about a week (3–21 days), about 20–30 percent of infected people develop the second phase of the disease , actual encephalitis, with fever and symptoms of encephalitis. Symptoms of encephalitis include:

• fever

• headache

• stiff neck

• photophobia

• nausea

• possible neurological symptoms, such as impaired consciousness, seizures or symptoms of paralysis.

The mortality rate from tick-borne encephalitis is low, less than 1% of those infected with the disease.

However, a large proportion of people who contract encephalitis will have long-lasting, and 2–10% even permanent, central nervous system symptoms.

Common after-effects:

• irritability

• memory and concentration difficulties

• hearing impairment

• limb paralysis

• muscle weakness.

Tick-borne encephalitis can be prevented by wearing clothing that covers the skin, using insect repellents, and getting a vaccine.

When traveling in areas where tick-borne encephalitis occurs

• wear light-colored, long-sleeved and long-sleeved clothing

• tuck your trouser legs into your socks

• wear high boots

• Use insect repellents applied to the skin on exposed skin.

After a walk in nature

• check your clothes for ticks attached to them

• Check your pet's fur, as pets can carry ticks indoors.

Because tick-borne encephalitis is transmitted within minutes of being bitten by a tick carrying the disease, it is especially important to pay attention to proper protection when traveling in risk areas.

A traditional once-daily tick bite does not effectively prevent tick-borne encephalitis. However, it is necessary to prevent Lyme disease. Since Lyme disease and tick-borne encephalitis are partly prevalent in the same areas, it is wise to always do a tick bite after visiting tick-borne areas.

The tick-borne encephalitis vaccination, which is part of the national vaccination program, is given free of charge to anyone who lives or stays for a long time in an area where the risk of tick-borne encephalitis is high.