When viruses don’t go viral: the importance of host phylogeographic structure in the spatial spread of arenaviruses

Many emerging infections are RNA virus spillovers from animal reservoirs. Reservoir identification is necessary for predicting the geographic extent of infection risk, but rarely are taxonomic levels below the animal species considered as reservoir, and only key circumstances in nature and methodology allow intrinsic virus-host associations to be distinguished from simple geographic (co-)isolation. We sampled and genetically characterized in detail a contact zone of two subtaxa of the rodent Mastomys natalensis in Tanzania. We find two distinct arenaviruses, Gairo and Morogoro virus, each spatially confined to a single M. natalensis subtaxon, only co-occurring at the contact zone’s centre. Inter-subtaxon hybridization at this centre and a continuum of quality habitat for M. natalensis show that both viruses have the ecological opportunity to spread into the other substaxon’s range, but do not, strongly suggesting host-intrinsic barriers. Such barriers could explain why human cases of an...诸多新发传染病均为源自动物贮存宿主（animal reservoirs）的RNA病毒跨种溢出事件。明确贮存宿主对于预测传染病风险的地理分布范围至关重要，但当前研究极少将分类学层级细化至动物物种以下的贮存宿主类群，且仅在特定自然条件与研究方法下，方能将病毒与宿主的固有关联与单纯的地理共分离（co-isolation）现象区分开来。 我们针对坦桑尼亚境内南非多乳鼠（Mastomys natalensis）两个亚类群（subtaxa）的接触带开展了采样，并进行了详细的遗传学特征分析。研究发现了两种截然不同的沙粒病毒（arenaviruses）：盖罗病毒（Gairo virus）与莫罗戈罗病毒（Morogoro virus），二者各自的空间分布仅局限于对应的一个南非多乳鼠亚类群，仅在接触带的中心区域存在共同检出的情况。 该接触带中心存在的亚类群间杂交现象，以及南非多乳鼠连续分布的优质栖息生境，表明两种病毒均具备向对方亚类群分布范围扩散的生态学条件，但实际并未发生扩散，这强烈提示存在宿主固有性的传播障碍。此类传播障碍或可解释为何某类人类感染病例的……