后大流行时期的生活253——基本传染数（R0）

• “R0”是什么

• “R0”的由来和意义
  

• “R0”的局限性

• 部分传染病的R0

  
  

一、“R0”是什么

• R0＜1，传染病将会逐渐消失。

• R0＞1，传染病会以指数方式散布，成为流行病。但是一般不会永远持续，因为可能被感染的人口会慢慢减少。部分人口可能死于该传染病，部分则可能病愈后产生免疫力。

• R0=1，传染病会变成人口中的地方性流行病。

  
  

图253-1 埃博拉和非典的传播R0展示

R0不是病原体的生物常数，它还受到其他因素的影响，例如环境条件和感染人群的行为。因此在不同传染源的传染性如果不重新计算就无法进行比较，同一种传染病过去的流行数值可能不适用于当前的爆发。鉴于R0实际上是由数学模型估算出来的数值，所以通常情况下在相关文献中给出的不同传染病的R0值仅在给定的语境中才有意义，其本身并不能估计感染在人群中传播的速度。

虽然R0存在一些局限性，但其仍是我们了解传染病传播能力的一项参考，这里整理了部分文献中的部分传染病R0信息（图253-2）。

图253-2 部分文献中的部分传染病R0值

实际上，由于既往感染或者疫苗接种，对于已经流行的传染病来说，总会有不同比例的人群在不同时间具备一定的免疫力，同时由于各种非药物措施的存在，所以现实中的流行流行情况往往会受到很多制约。

尽管R0似乎是一个简单的可以用来确定传染病传播动态以及新的疫情爆发时对公众健康造成的威胁的衡量标准，但针对不同传染病R0的计算和解释其实相当复杂。R0在大众媒体广泛传播的过程中，经常会以各种方式被误解和误用，不过R0仍然是一个有价值的流行病学概念，可以当做日常生活中不同传染病传播能力的一种参考。

以上就是本期分享的全部内容，如果有什么问题欢迎给我留言，也可以给我发送邮件（dzdyzj@126.com）

参考资料：

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