The virus replicates in the horse and salivary glands of the vector, the midge Culicoides imicola . Native horses harbour the virus and "fuel" Culicoides. Once, the virus was found only in Africa. Since 1987 it has re-appeared in Spain (as far north as Madrid) & Portugal where the vector occurs. The virus may be endemic there. In the recent Spanish outbreaks hundreds of horses have died or been destroyed. The presence of the virus in Spain is highly relevant to British veterinary surgeons because of the international traffic of horses to affected countries, for example, to Spain for the Barcelona Olympics.