Epidemics

A disease trying to become a pandemic would want to start small in some third world country in Africa. Then it wants to have minor symptoms that can spread itself without alerting the whole world to itself. Then it will begin to spread to other countries where it might slow down a little bit  because of the Hygiene and antibacterial products that most first world countries have. And then once everyone in the world is infected flip the kill switch and watch humanity burn to the ground.