A controversial field of research is "gain-of-function," in which scientists take a virus (like a strain of flu) and attempt to make it more dangerous, for example by making it transmissible in mammals when it had previously been solely an avian flu. The motivation is to learn how viruses might mutate in nature so that we can be prepared -- but what if those engineered "superbugs" escape the lab and start a pandemic? In this episode of Rationally Speaking, Harvard professor of epidemiology Marc Lipsitch argues that the risks outweigh the benefits, and that we should halt gain-of-function research as soon as possible.

Marc Lipsitch is Professor of Epidemiology with primary appointment in the Department of Epidemiology and a joint appointment in the Department of Immunology and Infectious Diseases. He directs the Center for Communicable Disease Dynamics, a center of excellence funded by the MIDAS program of NIH/NIGMS. He is also the Associate Director of the Interdisciplinary Concentration in Infectious Disease Epidemiology.