| 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. | 1993 | 8289690 |