Developer Valve announced today that the first downloadable content package for recently released Zombie shooter sequel Left 4 Dead 2 will be released in “early spring”.

This means that the package will be available on PC and Xbox 360 in May or April 2010.

Entitled “The Passing”, the package will see the original Left 4 Dead survivors meet up with those from Left 4 Dead 2 with players having the ability to control the new survivors.

It will also include a campaign, set in rural Georgia, which will follow the events in Left 4 Dead 2’s Dead Center campaign and will also feature a new firearm, melee weapon and a new kind of “uncommon foe” and new arenas for Survival, Scavenge and Versus modes plus a “new kind of co operative play”

“The Passing will become the most important campaign in the Left 4 Dead story, as all the Survivors are being called together in one campaign,” said Valve marketing VP Doug Lombardi. “It will also be a huge offering of new gameplay content, with something new for every game mode plus a new uncommon common and weaponry.”