Dan Werb, PhD, is an assistant professor in epidemiology at the University of California San Diego and the University of Toronto. He has received major grants from the National Institute on Drug Abuse, the Pierre Elliott Trudeau Foundation, and other organizations. His writing has appeared in publications such as the Believer and the Walrus, where his feature “The Fix” on new tactics for treating injection drug use won a Canadian National Magazine Award. He is based in San Diego and Toronto.