The Sars-CoV-2 coronavirus most likely originated in a bat in southern China and then jumped over to humans. The fact that this region in particular became the place of origin of the corona pandemic is possibly climate-related, as a study now suggests. Accordingly, the climate and vegetation in southern China have changed in the last 100 years in such a way that the region has become a hotspot for bats and their coronaviruses. Around 40 new bat species have settled there since then, and with them around 100 different viruses.
It is not yet clear via which animal the Sars-CoV-2 coronavirus jumped to humans. However, genetic comparisons suggest that the precursor of this pathogen once developed in bats. Several bat coronaviruses with a genetic makeup similar to Sars-CoV-2 have already been found in animals from the Yunnan province and neighboring areas in southern China. It is also known that bats are an abundant reservoir for viruses that are potentially pathogenic to humans: “Of all the mammalian orders, bats carry the highest proportion of all zoonotic viruses,” explain Robert Meyer from the University of Cambridge and his colleagues. On average, a bat harbors almost 2.7 types of virus, and a total of over 3000 different bat coronaviruses are known.
On the trail of climate-related shifts
An area with a particularly dense and species-rich bat population is therefore also a potential hotspot for coronaviruses: “An increase in local bat diversity can increase the likelihood that a coronavirus with potentially pathogenic effects for humans is present there, is transmitted or is transmitted developed in the region, ”say the researchers. They have therefore investigated whether and how the species distribution of bats has changed over the past 100 years and what role climate changes play in this. To do this, they first reconstructed the global natural vegetation at the beginning of the last century using climatic data in comparison to today’s conditions. Then, based on the bats’ typical requirements for their environment, they determined which bat species were present where, and compared this with today’s occurrence.
The comparisons showed that there are some areas around the world in which the conditions for bats have become more favorable – for example, because tropical bushland has given way to tropical savannah and deciduous forest. “As a result of climate change, the habitats of bats have shifted. The animals spread to new areas – and brought their viruses with them, ”explains Beyer. These areas include parts of Central Africa, some areas of Central and South America, but above all a large area around the southern Chinese province of Yunnan and adjacent areas of Laos and Myanmar.
40 more bat species
“In the last century, climate change in the likely area of origin of Sars-CoV-2 has made the habitat for bats much more attractive – and thus also for the many coronaviruses that these animals carry”, says Beyer. Specifically, around 40 more bat species live in Yunnan in southern China than they did 100 years ago. As a result, the number of bat coronavirus variants that occur there has increased by around 100. “This not only changed where the viruses were to be found, but also enabled new interactions with other animals through which harmful pathogens were transmitted or developed,” explains Beyer. The climatic changes could ultimately have contributed to turning Yunnan and the neighboring regions into hotspots for bat diversity and thus also hotspots for coronaviruses.
However, this climate change is not the only factor that makes habitats new hotspots for bats and their coronaviruses, as the research team emphasizes. Changes in land use and interventions in previously untouched natural areas also play a role in the distribution of species and human contact with potentially zoonotic viruses. Nevertheless, according to Beyer and his team, climate change could be directly responsible for the fact that the viral precursors of Sars-CoV-2 were able to develop and establish in southern China. “We know that climate change is accelerating the transmission of viruses in wildlife to humans,” says co-author Camilo Mora of the University of Hawaii at Manoa. “That should prompt us urgently to improve measures to reduce emissions.”
Source: Robert Meyer (University of Cambridge) et al., Science of the Total Environment, doi: 10.1016 / j.scitotenv.2021.145413