A viral infection (flavivirdae) of the central nervous system which is transmitted by ticks. Ticks usually feed on small rodents who are the main carriers of the virus. Transmission may also occur through the consumption of untreated milk. The incubation period is usually 1 to 2 weeks. The symptoms occur in two phases: the first involves symptoms of a general viral illness (fever, headache, nausea, aching muscles) followed by a period of remission and then central nervous system inflammation such as meningitis. However, many patients only suffer the first phase of the disease. See also Tick-borne encephalitis