Tick-borne encephalitis (TBE) is a viral infection usually transmitted by tick bites, though it can also be acquired by ingesting unpasteurized milk or milk products from cows, goats or sheep. Headache, fever and other flu-like symptoms begin suddenly 1 to 2 weeks after contact. These symptoms resolve after about a week, but in some cases the illness resumes after a few days of apparent recovery. This second phase can be very serious, with fever accompanied by neurological symptoms such as seizures, paralysis and coma resulting from brain infection.
TBE is found in eastern and central Europe. Russian spring-summer encephalitis (RSSE) is a form of TBE found in Siberia, northeast China and Korea. The European illness tends to be milder, with few deaths reported. Cases of RSSE are more often serious and fatal. It usually occurs in forest and rural areas, in the northern hemisphere from May through September, with incidence peaking in July.
Tick-borne viruses usually are isolated only from female ticks; usually there is no ill effect of viral infection on the tick.