Analysis of 179 new Ebola virus sequences from patient samples collected in Guinea between March 2014 and January 2015 shows how different lineages evolved and spread in West Africa. Supplementary information The online version of this article (doi:10.1038/nature14594) contains supplementary material, which is available to authorized users.

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 another M. natalensis-borne arenavirus, Lassa virus, are limited to West Africa.

It has been a long time since the world has experienced a pandemic with such a rapid devastating impact as the current COVID‐19 pandemic. The causative agent, severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), is unusual in that it appears capable of infecting many different mammal species. As a significant proportion of people worldwide are infected with SARS‐CoV‐2 and may spread the infection unknowingly before symptoms occur or without any symptoms ever occurring, there is a non‐negligible risk of humans spreading SARS‐CoV‐2 to wildlife, in particular to wild non‐human mammals. Because of SARS‐CoV‐2’s apparent evolutionary origins in bats and reports of humans transmitting the virus to pets and zoo animals, regulations for the prevention of human‐to‐animal transmission have so far focused mostly on these animal groups. We summarise recent studies and reports that show that a wide range of distantly related mammals are likely to be susceptible to SARS‐CoV‐2, and that susceptibility or resistance to the virus is, in general, not predictable, or only predictable to some extent, from phylogenetic proximity to known susceptible or resistant hosts. In the absence of solid evidence on the susceptibility and resistance to SARS‐CoV‐2 for each of the >6500 mammal species, we argue that sanitary precautions should be taken by humans interacting with any other mammal species in the wild. Preventing human‐to‐wildlife SARS‐CoV‐2 transmission is important to protect these animals (some of which are classed as threatened) from disease, but also to avoid establishment of novel SARS‐CoV‐2 reservoirs in wild mammals. The risk of repeated re‐infection of humans from such a wildlife reservoir could severely hamper SARS‐CoV‐2 control efforts. Activities during which direct or indirect interaction with wild mammals may occur include wildlife research, conservation activities, forestry work, pest control, management of feral populations, ecological consultancy work, management of protected areas and natural environments, wildlife tourism and wildlife rehabilitation in animal shelters. During such activities, we recommend sanitary precautions, such as physical distancing, wearing face masks and gloves, and frequent decontamination, which are very similar to regulations currently imposed to prevent transmission among humans. We further recommend active surveillance of domestic and feral animals that could act as SARS‐CoV‐2 intermediate hosts between humans and wild mammals.