Flu viruses have evolved proteins that let them break through mucus

Before viruses can infect cells, they must first get to them, often by traversing layers of the body’s protective mucus. Understanding how evolution optimised the influenza A virus for this slimy task could help us create new antiviral drugs.

If you just dropped an influenza A virus into mucus, natural diffusion would never carry it to cells fast enough to cause an infection, says Siddhansh Agarwal at the University of California, Berkeley. Influenza A viruses – the only influenza…