Valve have released a beta version of Dead Air for Left 4 Dead 2.

Besides adding melee weapons, they have made some changes to the 4th and 5th maps of the campaign.

Make sure to try some different strategies – especially in the finale.

Valve have also tried something new with the Scavenge map in this campaign. But giving nothing away?

 Cold Stream and the rest of the Left 4 Dead 1 maps will be out later this summer as part of the Cold Stream DLC.