For the first time, scientists have directly visualized in real-time structural changes in the surface protein of the influenza virus that may help the virus to fuse with and enter target cells before hijacking their functions. Researchers at Tufts University School of Medicine found that single molecules of the protein hemagglutinin (HA) that reside on the surface of the virus unfold to stretch toward target cells, then refold and try again 5 to 10 times per second. The discovery shows the flu virus to be more dynamic than previously thought and may help efforts to develop more effective vaccines and better understand other viruses such as Ebola, HIV, and SARS. The research appears in the journal Cell online June 28 and in print August 9.