甲型肝炎是一种全球性传染病,在发展中国家或地区,人群大多在儿童时期即被感染而获得免疫,但随着经济文化的发展,感染率逐步下降,易感人群增多,当传染源被引入后,即可引起流行或爆发流行。昆 Hepatitis A is a global epidemic. In developing countries and regions, most of the population is immunized during childhood. However, with the development of economy and culture, the rate of infection is gradually reduced and the number of susceptible people is increased. When it is transmitted After the source is introduced, it can cause epidemic or outbreak epidemic. Kun