An antiviral drug that inhibits a virus’ replication machinery selectively targets the most aggressive viruses, according to new research that looked at the infection of individual cells by a virus and the consequence of antiviral intervention. This new insight into the dynamics of an infection and the mechanism of an antiviral drug could not be seen by the typical approach of studying populations of cells. Researchers at Penn State, Duke University, and the University of Texas at Austin have developed a high-throughput system to study large numbers of single, infected cells that facilitated the new insight. A paper describing the results of the research appears in the journal Cell Reports.