A viral disease of sheep, capable of producing central nervous system manifestations. It occurs chiefly in the British Isles. Infections have been reported, although rarely, among persons working with sheep. In sheep the disease is usually biphasic with a systemic influenzalike phase, which is followed by encephalitic signs. In infected humans the first phase is generally the extent of the illness. The virus is a member of the Russian tick-borne complex of the group B arboviruses. Characteristics, diagnosis, and epidemiology are similar to those of other viruses of this complex. Animal virus Arboviral encephalitides