Toxoplasmosis Gondii. If it gets in a rat, the rat no longer becomes fearful of said cat. Now if we amplified this affect, and say put it in say... a human. The results should be the same, just on different things I.E. Guns and other large animals.
In the CDC article, they kept mentioning natural disasters, so that's really what the article is for. They just used the Zombie ploy to catch people's attention.