https://play.google.com/store/apps/details?id=com.miniclip.plagueinc
https://itunes.apple.com/us/app/plague-inc./id525818839?mt=8
The premise of the game is really morbid: your objective is to start a disease and try to spread it to every country in the world and kill everyone. You get points to mutate your virus or bacteria and make it harder to cure, easier to infect people, become more lethal.
You're presented with a map of the world (some regions' countries are grouped into one, but a lot of countries have their real borders and populations) and you decide what kind of plague to use, where to start and after that how to spread it and infect as many as possible and prevent the cure from being created before the end of humanity.
If your disease is too lethal too early, then it might kill off all the infected and that means you lose. Initially your disease can spread by land, air and sea but later on countries shut their borders, ports and airports and it becomes very difficult to spread.
For 1 dollar this is an amazing value in a game, you can play this for hours on end, you start off with only the option to create a bacteria, but you can unlock more types of pathogens as you go and upgrades to your diseases (or you can unlock everything faster by paying for the stuff).
I've put a couple of hours into it already and really surprised how good it is for the price and it does get more challenging as you get further in.
Edit: I've only played on Normal difficulty so far and failed twice to wipe out humanity with bacteria. Once I got to about 76% killed and the second time about 95%. It's hard to kill off countries that are far away and isolated (Greenland for example).
Rich countries fight diseases faster than poor countries as well.
Here's a video of the game:
http://www.youtube.com/watch?v=q0tK_C5JeX0
XBL Gamertag: ckmlb, PSN ID: ckmlb
