Valve have let fans have a play of the Swamp Fever campaign at Comic-Con in San Diego this weekend, subsequently showing off some new Infected.

The developer insists there are still yet more types of Special Infected to come, one of these being the ominous sounding Spitter, who spurts out a horrible burning substance and damages anything it touches.

There are a new set of zombies including riot cops who you can only kill from behind as they’re, of course, in riot gear. Then there’s mud men who crawl around the floor, even when underwater, which is fairly frequent and often uncomfortably close when you’re in a swamp yourself.

There are gauntlets too, which are a little like the sieges from the end of the levels in the first game. These require players to run as fast as they can through hoards of Infected in difficult to navigate locations. There’s a section in the campaign in and around a grounded plane and with a ferry. Another campaign, The Parish, involves a dash down a bridge.