The Last Sorcerer — Michael Jasper

"Magic: It can show up in the strangest places..."
An old man sleeping in a cardboard box in snowy Chicago holds the secret of sorcery in his head. Thanks to the damage done to him by using magic decades ago, he doesn't realize it. Most days he can't even remember his own name.
But when two teens try to jump him in an alley, the magic Words come back to him at last, and he "infects" the kids with magic. And soon Chicago has a wild epidemic of magic on its hands...
An earlier, but still self-contained version of the novel "A Sudden Outbreak of Magic," but with a slightly altered cast of characters and plotlines. Consider it the "alternate-world" version of the Contagious Magic story.