Tick-borne encephalitis
Cause
The tick-borne encephalitis (TBE) virus of the family Flaviviridae. Three subtypes of the causative agent are known: the European, the Far Eastern (spring-summer encephalitis) and the Siberian. Other closely related viruses cause similar diseases.
Transmission
Infection is transmitted by the bite of infected ticks or occasionally by ingestion of unpasteurized milk. There is no direct person-to-person transmission. Some related viruses, also tick-borne, infect animals such as birds, deer (louping-ill), rodents and sheep.
Nature of the disease
Infection may induce an influenza-like illness, with a second phase of fever occurring in 10% of cases. Encephalitis develops during the second phase and may result in paralysis, permanent sequelae or death. Severity of illness increases with age of the patient. The far-eastern subtype is believed to cause more severe symptoms and sequelae than the European subtype.
Geographical distribution
The European subtype is present in large parts of central and eastern Europe, particularly Austria, southern Germany and northern Switzerland, the Baltic states (Estonia, Latvia, Lithuania), the Czech Republic, Hungary and Poland; the far-eastern subtype is found from north-eastern Europe to China and Japan, and the Siberian subtype from northern Europe to Siberia. The disease is seasonal; most cases occur during April to November. The risk is highest in forested areas up to an altitude of about 1400 m.
Risk for travellers
Travellers during the summer months in countries or areas at risk, are particularly at risk when hiking or camping in rural or forested areas.
Precautions
Avoid bites by ticks by wearing long trousers and closed footwear when hiking or camping in countries or areas at risk. If a bite occurs, the tick should be removed as soon as possible.