Department of Ecology and Evolutionary Biology, University of California, Los Angeles, 610 Charles E. Young Drive South, Los Angeles, CA 90095, USA.
Philos Trans R Soc Lond B Biol Sci. 2013 Jun 24;368(1623):20120150. doi: 10.1098/rstb.2012.0150. Print 2013 Aug 5.
A recurring theme in the epidemiological literature on disease eradication is that each pathogen occupies an ecological niche, and eradication of one pathogen leaves a vacant niche that favours the emergence of new pathogens to replace it. However, eminent figures have rejected this view unequivocally, stating that there is no basis to fear pathogen replacement and even that pathogen niches do not exist. After exploring the roots of this controversy, I propose resolutions to disputed issues by drawing on broader ecological theory, and advance a new consensus based on robust mechanistic principles. I argue that pathogen eradication (and cessation of vaccination) leads to a 'vacated niche', which could be re-invaded by the original pathogen if introduced. Consequences for other pathogens will vary, with the crucial mechanisms being competitive release, whereby the decline of one species allows its competitors to perform better, and evolutionary adaptation. Hence, eradication can cause a quantitative rise in the incidence of another infection, but whether this leads to emergence as an endemic pathogen depends on additional factors. I focus on the case study of human monkeypox and its rise following smallpox eradication, but also survey how these ideas apply to other pathogens and discuss implications for eradication policy.
在疾病消除的流行病学文献中，一个反复出现的主题是，每种病原体都占据着一个生态位，消除一种病原体就会留下一个空缺的生态位，有利于新的病原体出现来取代它。然而，杰出的人物毫不含糊地拒绝了这种观点，他们表示，没有理由担心病原体的替代，甚至不存在病原体的生态位。在探讨了这一争议的根源之后，我通过借鉴更广泛的生态理论，提出了解决有争议问题的方案，并基于稳健的机制原则提出了一个新的共识。我认为，病原体的消除（以及疫苗接种的停止）会导致一个“空缺的生态位”，如果引入，原来的病原体可能会重新入侵。对其他病原体的影响将有所不同，关键的机制是竞争释放，即一个物种的衰落会使其竞争者表现得更好，以及进化适应。因此，消除可以导致另一种感染的发病率出现定量上升，但这是否会导致该感染成为地方性病原体，还取决于其他因素。我以人类猴痘及其在天花消除后上升的案例研究为重点，但也调查了这些想法如何适用于其他病原体，并讨论了对消除政策的影响。
