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

I have it, its free! Surprisingly good, best on a tablet, though.

ckmlb? Interesting. Who's next? stof, Kwaad, ArtofAngels?

Looks like a rip off of Pandemic 2, but since it's free on android I'll check it out.

Freaking awesomely disturbing game, got it for free on Android. Though a week after playing it I came down with Salmonella poisoning and spent 4 days in hospital, felt like I was getting smacked down with digital karma.

I've seen it on the App Store. I was hesitant to buy it at first but I might go for it later on.

Yep.

I beat every type on brutal except the final one. Though I did only play it once on the easiest setting.

Fun game.

EDIT on Android its still worth its price. You get rid of ads and the features it unlocks are VERY nice for the overall experience.

I've beat it on hard with everything. Fun game. Start in Russia.

India is better. More of the world (as well as more populace areas) has a 'warm' climate so its best to get the warm for free and only have to buy cold later on as you start to spread into lower populations in the colder areas.

My strategy doesn't usually need any heat advancements. You practically need cold though if you want to kill greenland.