Ignacio González Bravo
Research director at the Laboratory of Infectious Diseases and Vectors: Ecology, Genetics, Evolution and Control (MIVEGEC) of the French National Center for Scientific Research (CNRS).
The team led by Dr Shweta Bansal has analysed the projected evolution of zoonosis risk from the present to 2070 under different scenarios of climate change, land-use change (from forest or jungle to crops, for example) and mammal migration.
The results show that the changes will lead to a large number of new contacts between animal species that have never shared habitats before. This cohabitation will make it possible for viruses infecting one species to gain access to a new host species and successfully jump species. The researchers predict that the hotspots for these new contacts are in the ecologically rich high-altitude regions of Asia and Africa. The researchers also show that bats are likely to be involved in the vast majority of new contacts between mammalian species.
For humans, the researchers show that the centres of new contacts and possible zoonoses until 2070 are centred in tropical areas with high population densities and geographical variations in altitude, such as the Sahel, the plateaus in Ethiopia, the Rift Valley, India, eastern China, Indonesia or the Philippines.
The results suggest that many of these habitat changes are already underway, so that the potential for new interspecies contacts and the likelihood of zoonoses will increase in the coming decades.
Dr Shweta Bansal's team's projections can only include the virus-host relationships we know about, of course. For many poorly known viruses that are potentially dangerous to humans, such as the Usutu virus, or for viruses for which we do not know the source and host in the wild (such as the Zaire Ebola virus), accurate forecasts cannot be made. Likewise, we do not yet fully understand why some species jumpers are successful and can lead to pandemics (such as HIV or SARS-CoV-2) and eventually become endemic (such as other human coronaviruses), while many others are unable to establish in the new species and are fortunately restricted to epidemic outbreaks. So we cannot yet predict how many of these new contacts and possible zoonoses will lead to local or global health emergencies.
The positive side of this work is that it identifies potential foci of new contacts between mammalian species. In this way, epidemiological surveillance can focus on potential high-risk species, in areas of high human density and land-use boundaries.