There are more than 3 million U.S. cases per year of the flu. It is an extremely common infection that can be deadly, especially in high-risk groups. While proper hygiene is to cover your mouth when you cough or sneeze, people don't always do that, almost guaranteeing that the tiny droplets of contagion will find a new host to infect. You can't always stay away from people who are sick either, so this condition just keeps going, relying on the variants...