Although many people think of the flu as a mild annoyance that we have to deal with each winter, it can actually be a dangerous disease. During annual influenza epidemics in temperate climate zones, an estimated 5-15% of the population become infected and an average of 2-10% of the population develop clinical influenza. The WHO estimates that these annual epidemics result in between 3 and 5 million cases of severe illness and between 250,000 and 500,000 deaths every year around the world. Most influenza deaths in industrialized countries occur among the elderly over 65 years of age. As a matter of fact, in developed countries, seasonal influenza annually claims more lives than traffic accidents.