What is the reservoir for the ebolavirus? According to the CDC, the natural reservoir host of ebolaviruses remains unknown. However, on the basis of available evidence and the nature of similar viruses, researchers believe that the virus is zoonotic (animal-borne), with bats being the most likely reservoir. Four of the five subtypes occur in an animal host native to Africa. A great many similar species are probably associated with the Reston virus, the virus that so far seems to attack nonhuman primates rather than human beings. The Reston virus was isolated from infected cynomolgous mokeys that were imported to Italy and the United States from the Philippines. Several workers in both the Philippines and in United States holding facility became infected with the Reston virus. They did not, however, become ill with Ebola. This is being cited as substantiation that the Reston virus appears to cause disease only in nonhuman primates. With the exception of several laboratory contamination cases (one in England and two in Russia), all reported cases of human illness or death appear to have occurred in Africa.