Plague Inc is an awesome iOS game that involves you controlling different diseases, including viruses, fungi, parasites, prions, and fictional diseases, such as neurax worms, and necroa viruses. When you start, you choose what country to infect, and with DNA points, you can upgrade transmissions, symptoms, and abilities to try to infect and
kill every human on
Earth. It has generally
pretty popular, on the App Store and extremely fun.