Risk factors for the evolutionary emergence of pathogens
Risk factors for the evolutionary emergence of pathogens
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DOI：
10.1098/rsif.2010.0123
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发表时间：
2010-10-06
影响因子：
3.9
通讯作者：
Day, T.
中科院分区：
文献类型：
--
作者：
Alexander, H. K.;Day, T.
最近爆发的新型传染病（例如SARS、H1N1流感）凸显了跨物种病原体传播的威胁。当病原体首次引入种群时，通常很难适应新宿主，必须进化才能避免灭绝。理论论证和实证研究提出了多种因素来解释为什么一些病原体出现而另一些病原体不出现，包括宿主接触结构、病原体适应途径和突变率。使用多类型分支过程，我们模拟了通过多种菌株进化的引入病原体的传播。扩展以前的模型，我们使用基于网络的方法将宿主接触模式与病原体传播性分开。我们还允许任意的自适应路径。这些概括导致了关于假设的风险因素的影响的新颖预测。病原体的适应性取决于其传播的宿主群体，而“最危险”的接触分布和适应性途径则取决于初始传播能力。出现概率对突变概率和所需的自适应步骤数量敏感，大的自适应步骤（例如同时点突变或重组）可能会产生巨大的影响。在大多数情况下，增加总体突变概率会增加出现的风险；然而，当存在有害突变时，就会出现明显的例外。
Recent outbreaks of novel infectious diseases (e.g. SARS, influenza H1N1) have highlighted the threat of cross-species pathogen transmission. When first introduced to a population, a pathogen is often poorly adapted to its new host and must evolve in order to escape extinction. Theoretical arguments and empirical studies have suggested various factors to explain why some pathogens emerge and others do not, including host contact structure, pathogen adaptive pathways and mutation rates. Using a multi-type branching process, we model the spread of an introduced pathogen evolving through several strains. Extending previous models, we use a network-based approach to separate host contact patterns from pathogen transmissibility. We also allow for arbitrary adaptive pathways. These generalizations lead to novel predictions regarding the impact of hypothesized risk factors. Pathogen fitness depends on the host population in which it circulates, and the 'riskiest' contact distribution and adaptive pathway depend on initial transmissibility. Emergence probability is sensitive to mutation probabilities and number of adaptive steps required, with the possibility of large adaptive steps (e.g. simultaneous point mutations or recombination) having a dramatic effect. In most situations, increasing overall mutation probability increases the risk of emergence; however, notable exceptions arise when deleterious mutations are available.