The course of virologist Charlie Rice’s career changed with one phone call in 1989. Then at Washington University in St. Louis, Rice was the country’s leading yellow fever expert. The voice on the other end of the line belonged to Stephen Feinstone, an FDA scientist asking about a vaccine for the disease that had just won agency approval. Yellow fever virus is a flavivirus. Feinstone wanted to know if Rice could help develop a vaccine to protect against another flavivirus: hepatitis C. “I can get interested in pretty much anything, I guess,” says Rice.