The “Common Flu” occurs every year and everywhere. An epidemic by definition means an infectious disease that develops and spreads rapidly in a community. The "Common Flu,” a seasonal disease resulted from antigenic variation in the influenza virus, has an infection rate of 10%. The peak of seasonal influenza in Taiwan usually occurs every December to March. Most patients can recover in two to seven days and generate antibodies. However, it will cause complications such as bronchitis, pneumonia, and so forth to the elderly, children, and those suffering from diabetes or cardiovascular and pulmonary diseases. The mortality rate is less than 0.1%. "Super Flu," a disease that simultaneously breaks out in many countries and spreads rapidly worldwide with the flow of population, will occur every ten to fifty years and appear anytime in a year. The reason of its occurrence lies in the great antigenic variation in influenza viruses that makes people unable to be protected by antibodies. It has an infection rate reaching 20-50%, and can result in severe symptoms at any age. "Super Flu" is usually accompanied by many infected cases and more severe symptoms, causing a high mortality rate.