By solving a long-standing puzzle about how the influenza virus assembles its genetic contents into infectious particles that enable the virus to spread from cell to cell, scientists have opened a new gateway to a better understanding of one of the world’s most virulent diseases. This insight into the genetic workings that underpin infection by flu, reported in the Proceedings of the National Academy of Sciences, provides not only a better basic understanding of how flu and other viruses work, but holds significant promise for new and improved vaccines and drugs to combat the disease by exposing the genetic trick it uses to form virus particles.