Infected is a fast-paced third person comedy zombie shooter. The focus is on a humorous plot and combo-based zombie killing.

It's Christmas time in New York and Zombies have come to ruin the festivities. As New York Cop Agent Stevens, you find out that not only are you immune to the zombie virus, but your blood is actually so powerful, it will make a zombie explode.

The main focus of the gameplay is shooting holes in the zombies until they are weak enough for you to fire a vial of your own blood into them, causing an explosion. Weaken enough zombies, fire a blood vial into one, and watch the chain reaction as exploding zombies send your anti-zombie blood onto other zombies.

The game was one of the first online PSP games, and featured a mode where defeating an opponent would give them your virus, and force their avatar online to look like your avatar. If they in turn defeated someone, your virus would be passed onto them as well. At any time you could look at a world map to see where on earth your strain of virus had travelled.