They have medicine resistant diseases all over the planet, and as long as medical research finds meds that kill diseases the diseases will find ways around it, that is Darwins fault I guess as he the one that figured it out as much as anybody, hell there is even a med resistant malaria over on the c\Cambo/Thai border, how long before it gets to Central??
Thats what you get for breaking Mother Natures Rules and she is a nasty mean bitch, kinda like Mustavaclit, Mother do not want you fucking serious, only for fun and as long as the head count go up she will continue to try to kill some off.