one word baby, retcon!!!
If your reffering to Marvel Zombies, not to worry. Morbius the Living Vampire, Machine Man and Howard the Duck found a cure for the virus in Marvel Zombies 5. But they only cured Werewolf by Night, and that's in the mainstream universe. I've no idea what happened to Headpool, and as for the rest of the zombies? They've been locked in a time loop by Uatu. I'm not sure if that means Headpool will keep showing up over and over again in the mainstream universe, but I hope not. Pirhana and several fishmen were killed by the virus, and so was Siege, a version of Deathlok. And Wundagorr (or whatever his name is) was infected and quarantined. Also, if Simon Garth lets the cloud out, that spells the end. It won't bring zombies, but the rain will kill us all to quote Slipknot. :)