Why influenza evolves annually

This year’s flu season has begun more than a month earlier than usual, with a mutated strain spreading widely among younger people and expected to drive a wave of hospital admissions as it reaches the elderly. Science editor Ian Sample speaks to Madeleine Finlay about what we know so far and Prof Ed Hutchinson of the University of Glasgow explains how people can best protect themselves and each other. Help support our independent journalism at theguardian.com/sciencepod