By entering the cell, as opposed to fusing with the cell on the cell membrane—which many other viruses do—the influenza virus hides from the immune system. The body’s defenses cannot find it and kill it. Inside this vesicle, this bubble, shape and form shift and create new possibilities as the hemagglutinin faces a more acidic environment. This acidity makes it cleave in two and refold itself into an entirely different shape. The refolding process somewhat resembles taking a sock off a foot, turning it inside out, and sticking a fist in it. The cell is now doomed.
