The explosion of Asia’s population really occurred when Western medicine significantly increased their lifespans while reducing their infant mortality; it will be interesting to see how this plays out in places where people still bathe in sewage...
How about Africa and the Middle East? To quote Tom Lehrer, "Are they grateful? No they're spiteful and they're hateful."
Most of the new strains of influenza appear in Asia because people live in close proximity with ducks, chickens and pigs, often letting them spend the winter in the living room or a stall near the house.