International travel and health

Tick-borne encephalitis

Cause

Tick-borne encephalitis virus (TBEV) of the family Flaviviridae. Three subtypes of the causative agent are known: the European (Western), the Far Eastern (spring-and-summer encephalitis) and the Siberian.

Transmission

TBEV is transmitted by the bite of infected ticks (which often remain firmly attached to the skin for days) or occasionally by ingestion of unpasteurized milk. There is no direct person-to-person transmission.

Nature of the disease

Infection may induce an influenza-like illness followed, in about 30% of cases, by high fever and signs of central nervous involvement. Encephalitis developing during this second phase may result in paralysis, permanent sequelae or death. Severity of illness increases with age of the patient.

Geographical distribution

Tick-borne encephalitis (TBE) tends to occur focally even within endemic areas. Currently, the highest incidences of clinical cases are being reported from foci in the Baltic States, the Russian Federation and Slovenia. High incidencesare also reported from foci in the North-Western Federal Area of the Russian Federation. Other countries that have reported cases within their territories, or that are considered to be at risk because of focally high prevalence of the virus in ticks, include Albania, Austria, Belarus, Bosnia, Bulgaria, China, Croatia, Denmark, Finland, Germany, Greece, Hungary, Italy, Mongolia, Norway, Poland, the Republic of Korea, Romania, Serbia, Slovakia, Slovenia, Sweden, Switzerland, Turkey and Ukraine.

Risk for travellers

Travellers to endemic areas may be at risk during April to November. The risk is highest when hiking or camping in forested areas up to an altitude of about 1500 m.

Precautions

Prevent blood-feeding ticks from becoming attached to the skin by wearing appropriate clothing, including long trousers and closed footwear, when hiking or camping in countries or areas at risk. The whole body should be inspected daily and attached ticks removed as soon as possible. The consumption of unpasteurized dairy products should also be avoided in those areas.

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