The disease detectives who solve the world’s strangest outbreaks

In 1999, hikers on Vancouver Island suddenly began falling mysteriously ill. Doctors found strange nodules growing on their lungs, and several people died as cases mounted over the next few years. The culprit was Crypotoccus gattii, a microscopic fungus that typically lives on rotting logs in tropical rainforests and that had somehow found its way thousands of miles north.

“We had this new fungus showing up in the Pacific Northwest that wasn't supposed to be there,” recalls molecular epidemiologist David Engelthaler, who was called in by the U.S. Centers for Disease Control and Prevention (CDC) to investigate the outbreak. The immediate question: “How on earth did it get there?”

Engelthaler and his fellow investigator, microbiologist and immunologist Arturo Casadevall, delved into gene