what is one general theory for the origin of AIDS

In the fourth part of the book, the narrative shifts to the summer of 1993 and the author’s own visit to Mount Elgon and Kitum Cave. At the beginning of his journey, Preston notes that the road he is taking to Mount Elgon is part of the Kinshasa Highway, also known as the “AIDS highway.” The road cuts through the middle of Africa and, as the author recalls from his childhood, was a rarely used dirt road until it was paved in the 1970s. Soon afterward, the AIDS virus started to appear in the towns running parallel to the highway.