Most emerging and re-emerging infectious diseases stem from viruses that naturally circulate in non-human vertebrates. When these viruses cross over into humans, they can cause disease outbreaks, epidemics and pandemics. While zoonotic host jumps have been extensively studied from an ecological perspective, little attention has gone into characterizing the evolutionary drivers and correlates underlying these events. To address this gap, we harnessed the entirety of publicly available viral genomic data, employing a comprehensive suite of network and phylogenetic analyses to investigate the evolutionary mechanisms underpinning recent viral host jumps. Surprisingly, we find that humans are as much a source as a sink for viral spillover events, insofar as we infer more viral host jumps from humans to other animals than from animals to humans. Moreover, we demonstrate heightened evolution in viral lineages that involve putative host jumps. We further observe that the extent of adaptation associated with a host jump is lower for viruses with broader host ranges. Finally, we show that the genomic targets of natural selection associated with host jumps vary across different viral families, with either structural or auxiliary genes being the prime targets of selection. Collectively, our results illuminate some of the evolutionary drivers underlying viral host jumps that may contribute to mitigating viral threats across species boundaries.

大多数新出现和重新出现的传染病源于在非人类脊椎动物中自然传播的病毒。当这些病毒传染给人类时，它们可能会导致疾病暴发、流行病和大流行。虽然从生态角度对人畜共患宿主跳跃进行了广泛研究，但很少有人关注这些事件背后的进化驱动因素和关联性。为了解决这一差距，我们利用了全部公开的病毒基因组数据，采用一套全面的网络和系统发育分析来研究支持最近病毒宿主跳跃的进化机制。令人惊讶的是，我们发现人类既是病毒溢出事件的源头，又是病毒溢出事件的汇点，因为我们推断，从人类到其他动物的病毒宿主跳跃多于从动物到人类的病毒宿主跳跃。此外，我们证明了涉及假定宿主跳跃的病毒谱系的高度进化。我们进一步观察到，对于宿主范围更广的病毒来说，与宿主跳跃相关的适应程度较低。最后，我们表明，与宿主跳跃相关的自然选择的基因组目标在不同的病毒家族中有所不同，结构基因或辅助基因是选择的主要目标。总的来说，我们的结果阐明了病毒宿主跳跃背后的一些进化驱动因素，这可能有助于减轻跨物种边界的病毒威胁。