Y: The Last Man, Vol. 1: Unmanned by Brian K. Vaughan

In the summer of 2002, a plague of unknown origin destroyed every last sperm, fetus, and fully developed mammal with a Y chromosome--with the apparent exception of one young man and his male pet. Now, aided by the mysterious Agent 355, the last human male Yorick Brown must content with dangerous extremists, a hoped-for reunion with a girlfriend on the other side of the globe, and the search for exactly why he's the only man to survive.