Tick-borne encephalitis is caused by the TBE virus (Flavivirus, group B) which is also called Hypr virus. It is a disease clinically similar to Russian spring-summer encephalitis. A frequent route of infection is oral, by drinking the milk of infected domestic animals. The main vector is Ixodes ricinus, a tick found throughout Europe, including Turkey, and the Atlas region of North Africa. The TBE virus has a tendency to spread westwards throughout the area of vector distribution. In Austria it is a serious menace and it has more recently widely occurred in West Germany, where mortalities were initially high. I. ricinus is also associated with louping ill.