Not quite the scariest disease ever.

As if Ebola and Bird Flu weren't enough to worry about, apparently there's a stealth parasite in town that we've all been living with unawares, Toxoplasma. From the New York Times (where else?):

This single-celled pathogen infects over half the world's population, including an estimated 50 million Americans. Each of Toxoplasma's victims carries thousands of the parasites, many residing in the brain. As if that were not enough of an accomplishment, Toxoplasma is equally adept at infecting all other warm-blooded animals, as disparate as chickens and kangaroos.

Though scientists believe the parasite is usually harmless, it appears that it might be responsible for a myriad of problems later in life. Moreover, the article is filled with interesting tidbits like how a parasite evolves to target cats (Taxoplasma needs cats to reproduce--no joke) and how parasites can impact behavior.