流行性感冒(流感)是一种最常见的传染病。病原为流感病毒,分甲、乙、丙三型,最主要的是甲型,其致病力强,易发生变异,常引起地区性流行或世界性大流行。流感一般为上呼吸道粘膜的表面感染,病毒不进入血流。临床症状大多典型,但由于各种因素的影响,临床表现也有差异。少数情况下流感病毒进入血流累及全身各个脏 Influenza (flu) is one of the most common infectious diseases. Pathogenic influenza virus, points A, B, C three types, the most important is A, its strong virulence, prone to mutation, often causing a regional epidemic or a worldwide pandemic. Flu is usually the upper respiratory tract mucosal surface infection, the virus does not enter the bloodstream. Most of the typical clinical symptoms, but due to various factors, the clinical manifestations are also different. In a few cases, the flu virus enters the blood stream and affects the whole body