Plague Inc. for iPhone
is a game in which you must create the perfect infection to eliminate the world population. You create the plague by using viruses and bacteria, and the game also allows you to select the country that you would like to attack.
The longer that your plague lasts, the more time it will have to mutate and become resistant to treatment. You will, then, have the chance to infect other areas, while controlling the speed and strength of the attack.
The game is free to play, but includes expansion packs that can be purchased. You can also purchase the expansion pack bundle at $14.99.