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传阅:“群体免疫”之前世今生

袁越

自然状态下的传染病

一个人得了某种急性传染病,多数情况下只有两种结局:死亡或者免疫。前者很好理解,后者指的是被感染者的免疫系统“认识”了这个病原体,下次再遇到它的话就不会中招了。
只有在少数情况下,急性传染病才会转变成慢性传染病,比如HIV病毒反转录成DNA之后整合进了宿主的基因组之中,或者乙肝病毒进入肝细胞后转变成“共价闭合环状DNA”(cccDNA),躲进了宿主的细胞核之中。这两种情况都比较罕见,本文不再讨论。

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