Commonly known as the flu, influenza is usually transmitted through the air like tuberculosis but sometimes through direct contact with contaminated surfaces. Every year during what's called "the flu season" tens of thousands of people get the flu. Despite feeling all achy and lousy for several days, most people eventually beat the virus and recover just fine. Despite the fact that effective and safe vaccines have been available and used for more than 60 years, influenza causes 250,000-500,000 deaths every year. Elderly people and those with chronic medical conditions are at particular risk of developing serious illness.