Valve today announced that nearly a half million members of the Left 4 Dead 2 (L4D2) community have voted to add a permanent new Mutation (aka game mode) to L4D2; Realism Versus. Realism Versus combines the rules of Versus and Realism Modes to create a Versus game that requires the best in Survivor teamwork.

With the release of the DLC "The Passing" last month, L4D2 has seen weekly new Mutations released every Friday. The excitement and response to Realism Versus was so overwhelming a Poll was added for the in-game blog which simply asked: "Should the Mutation be permanent?"

This week's Mutation is "Follow the Liter." The rules of Scavenge have changed. Only one group of cans spawn at a time, so survivors know exactly where to go. There is only one problem; the Infected know exactly where they are going.

The weekly Mutations are available to all owners of Left 4 Dead 2's "The Passing" DLC, available on PC and Xbox 360.

The new mutation up is called "Follow the Liter" and it's scavenger with only a single set of gas spawning at a time. Kinda directs the survivor to a single location, but it also means that the infected know where the survivors are going to be headed. Could be a cool take on it.