If you're looking for the best iPhone and iPad paid game app and you haven't downloaded Plague yet, stop everything and head over to the app store now — you want this game.

Plague is a strategy/simulation game that allows you to control a plague. Your goal is to infect the entire world with the disease before anyone comes up with a cure. The gameboard is essentially a world map and you begin by choosing the country where your plague will start off in.

Every decision you make in Plague informs the progression of gameplay. For instance, if your plague starts off somewhere hot like South Africa, you'll adapt very different symptoms, resistances and transmission vectors than if your plague starts in, say, Greenland.

Plague has a unique history as one of the most successful paid iPhone and iPad apps in App Store history. Debuting in 2012, the game comes from English studio Ndemic Creations, which is a one-man show created entirely by James Vaughan.

The paid app has been downloaded more than 10 million times and in 2012, it was a runner-up for IGN's Overall Best Strategy Game.

Plague is noteworthy for the realism with which it simulates a pandemic. In fact, the game is so realistic, the CDC invited Vaughan to speak in March.

Following the meeting, the CDC's Ali S. Khan posted the following on the organization's official blog:

"I became interested in Vaughan's game as a tool to teach the public about outbreaks and disease transmission because of how it uses a non-traditional route to raise public awareness on epidemiology, disease transmission, and diseases/pandemic information. The game creates a compelling world that engages the public on serious public health topics."