So there's three possibilities: 1) He wasn't in a coma for a month, 2) He was in a coma for a month, but something weird is going on, or 3) The writers didn't think it through. But how? They didn't starve to death. If they were barricaded, they were not among those who were going to die of Captain Trips. Did they all get a little bite, but avoid being devoured until they died?