The origin of HIV-1, the AIDS virus.

This article proposes a series of experiments to determine if cows and sheep could be used as animal models for HIV-1, the AIDS virus. To justify this effort, a substantial case is presented that HIV-1 is a natural recombinant of Bovine Leukemia Virus (BLV) and Visna Virus. This natural recombinant may have been inadvertently transferred to humans through the Intensified Smallpox Eradication Program conducted in sub-Saharan Africa in the late 1960s and most of the 1970s.