The zombie ant fungus attacks the brain of the ant growing inside (and outside) of its head causing it to "march to its death at a mass grave near the ant colony, where the fungus spores erupt out of the ant's head." How awesome is that?! And how freaky is it that real life nature can create something horror film producers thought they had a lock on?
Yet there already seems to be a cure, or at least a parasite the debilitates the fungus preventing it from spreading and allowing a colony of infected ants to survive -- presumably as zombies. Apparently the spores which spread the fungus are castrated by the parasite so they're unable to spread and infect more of the colony.
The article linked to above says "even though there are a lot of dead and infected zombie ants in the neighborhood, only a few of the spores of the zombie-ant fungus will become mature and able to infect healthy ants." Seems to me that we need the Zombie Research Society to look into how the parasites cripple the spores in ants and apply that to the spread of the zombie virus in humans. Moreover, it appears that zombification is not just a viral infection and we need to keep an eye out for such other types of pollination that lead to a mass outbreak.
It is good to know though that while nature can, in fact, create a true zombie outbreak, it also creates a defense against it as well. As always nature keeps things in balance.