Zoonotic emergence and the overlooked case of cities

Zoonotic emergence requires spillover from animals to humans, hence animal-human interactions. A lot has been emphasized on human intrusion into wild habitats (e.g., deforestation, hunting) and the development of agricultural and farming activities. However, the highly human-modified urban and peri-urban socio-ecosystems are also of great concern due to huge amounts of pet, domesticated and wild animals (e.g., birds, rodents and bats) that live in very close contact to very dense human populations. This adds to the existence of wet wildlife markets, urban parks and wastelands, zoos and even labs, where spillover from wildlife to humans may also occur. Furthermore, cities are transport hubs that form hotspots of import/export of living resources including animals, thus potentially promoting rapid and wide-scale spread of reservoir and vectors, hence pathogens, as well as pathogen admixture through viral recombination or bacterial plasmid exchanges. Finally, cities are deeply modified environments where living organisms, including reservoirs, vectors and pathogens, undergo strong selective pressures, thus opening the gate to evolutionary novelties, hence potential new infectious threats. As such, we believe urban socio-ecosystems should be paid more attention in terms of drivers of zoonotic emergence in humans needing adapted surveillance and mitigation. Accordingly, we propose and discuss several avenues of research and examples of actions that could be tested or generalized (e.g., focus on hotspots of emergence risks like informal settlements, wet markets or transport hubs; development of participative surveillance programs; shift towards inter-sectoral academic courses; massive investment into education and community information) in order to operationalize effective zoonotic surveillance. We advocate that this would allow ones to add emergence-preventive and early warning to usual outbreaks response strategies, thus significantly improving our collective ability to prevent zoonotic emergence and subsequent pandemics.