Nathanson N
Department of Microbiology, University of Pennsylvania, Philadelphia, PA, USA.
Arch Virol Suppl. 2005(19):3-15. doi: 10.1007/3-211-29981-5_2.
In this review, I use the term "perpetuation" for persistence of a virus in a population, since this is a different phenomenon from persistence of a virus in an infected host. Important variables that influence perpetuation differ in small (<1000 individuals) and large (>10,000) populations: in small populations, two important variables are persistence in individuals, and turnover of the population, while in large populations important variables are transmissibility, generation time, and seasonality. In small populations, viruses such as poliovirus that cause acute infections cannot readily be perpetuated, in contrast to viruses such as hepatitis B virus, that cause persistent infections. However, small animal populations can turnover significantly each year, permitting the perpetuation of some viruses that cause acute infections. Large populations of humans are necessary for the perpetuation of acute viruses; for instance, measles required a population of 500,000 for perpetuation in the pre-measles vaccine era. Furthermore, if an acute virus, such as poliovirus, exhibits marked seasonality in large populations, then it may disappear during the seasonal trough, even in the presence of a large number of susceptible persons. Eradication is the converse of perpetuation and can be used as a definitive approach to the control of a viral disease, as in the instance of smallpox. Therefore, the requirements for perpetuation have significant implications for practical public health goals.
在本综述中，我使用“持续存在”一词来表示病毒在人群中的存续情况，因为这与病毒在受感染宿主中的持续存在是不同的现象。影响持续存在的重要变量在小规模（<1000人）和大规模（>10000人）人群中有所不同：在小规模人群中，两个重要变量是个体中的持续存在以及人群的更替，而在大规模人群中，重要变量是传播性、代时和季节性。在小规模人群中，像脊髓灰质炎病毒这种引起急性感染的病毒不容易持续存在，这与像乙型肝炎病毒这种引起持续性感染的病毒形成对比。然而，小型动物种群每年的更替可能很大，这使得一些引起急性感染的病毒能够持续存在。急性病毒的持续存在需要大量的人类人群；例如，在麻疹疫苗出现之前的时代，麻疹病毒需要50万人口才能持续存在。此外，如果一种急性病毒，如脊髓灰质炎病毒，在大规模人群中表现出明显的季节性，那么即使存在大量易感人群，它也可能在季节性低谷期消失。根除是持续存在的相反情况，并且可以用作控制病毒性疾病的决定性方法，就像天花的例子一样。因此，持续存在的条件对实际的公共卫生目标具有重要意义。
