流行性感冒(以下简称流感)在人群中经常发生流行,是由于流感病毒的抗原性变异所致,尤其是甲型流感病毒更是如此。近四十年来,甲型流感病毒发生过四次大的变异,出现过甲_0、甲_1、甲_2、甲_3四个亚型,每次变异都引起一次世界性流行,且每个亚 Influenza (hereinafter referred to as influenza) epidemic in the crowd often occurs due to the antigenic variation of influenza virus, especially the influenza A virus is even more so. In the recent four decades, there have been four major variations in the influenza A virus. Four subtypes of A, A, A, A, and A have emerged. Each mutation has caused a worldwide epidemic. Every Asian