When most people think of dangerous infections, they picture bacteria or viruses. But for infectious disease specialists like Peter Chin-Hong, one of the most insidious threats lurking in hospitals and clinics today is fungal.

Chin-Hong¡¯s case list is long: a healthy 29-year-old marathon runner from California¡¯s Central Valley whose heart lining was invaded by Coccidioides, a soil-dwelling fungus; a lung transplant recipient coughing up mold nodules ¡ª fungal growths scattered throughout his lungs ¡ª after stopping antifungal medication; and a 45-year-old woman with poorly controlled diabetes, infected by a black fungus that destroyed part of her face and spread to her brain. Despite multiple surgeries and treatment, she died in the hospital.

"These aren¡¯t rare anymore,¡± said Chin-Hong, associate dean and professor of medicine at the University of California, San Francisco. "We¡¯re seeing them every day.¡±