This mathematical research paper by Philip Munz, Ioan Hudea, Joe Imad, and Robert J. Smith? (yes, Robert spells his last name with a “?”), applies mathematical models of epidemic spread to a hypothetical zombie “epidemic”. Their conclusion:
[A] zombie outbreak is likely to lead to the collapse of civilization, unless it is dealt with quickly. While aggressive quarantine may contain the epidemic, or a cure may lead to coexistence of humans and zombies, the most effective way to contain the rise of the undead is to hit hard and hit often. As seen in the movies, it is imperative that zombies are dealt with quickly, or else we are all in a great deal of trouble.
In other words, those movies where nearly everybody is turned into a zombie except for a small band of survivors, but then the small band of survivors figures out a way to turn the tables and vanquish the zombie horde? In actuality, that could never happen.
The paper was featured in the Wall Street Journal online here and Wired magazine here, as well as many other online sites. Addendum: the paper also appeared in the NY Times “The Year in Ideas” issue, 2009 edition.