In less than a century, the foothold has become a stranglehold. Looking back, we can see that instability of the environment was a major factor in the rise of today's AIDS epidemic. Apparently the virus circulated almost exclusively among non-human primates. But as humans decimated these hosts they offered the virus an abundant alternative host. The virus made use of the opportunity and depends on us for survival.
Human interference continues and grows with the human population.
Our intrusion on more and more monkey and ape habitats, especially the rainforest communities, has convinced some scientists that monkeys could vanish from the wild by the end of the twenty-first century. They will not simply vanish too. A few will survive in zoos with their remaining natural hosts. However, most of the retroviruses will acept the opportunity to jump to new hosts, most probably the human population. To survive and spread, they will adapt and cause disease.