HIV was just a local disease and not worthy of much note until the roads and then the airplanes came. Once that happened, it got exported and the rest of the world got a look at just how diabolical a retrovirus could be: hiding for years while a person was able to infect others, hiding beyond the blood/brain barrier where drugs couldn't kill it, and killing by opening a door to other infections, keeping its own little viral hands clean.
The end of oil could be the end of exporting these emerging diseases from emerging economies. I don't know what else will. Until then, outfits like WHO are going to have to figure out just what they are and whether they can be prevented or treated.