More risk of new diseases in a warmer world

It is estimated that 10,000 viruses are in principle capable of infecting humans, but most of them currently only circulate among wild mammals. Climate change could change that, show US researchers in Nature†

Warming causes species to migrate when it is too hot underfoot. The viruses they carry also travel with them. In their new habitat, they can jump to animal species with which they would never have come into contact with otherwise. Global warming could cause more than 15,000 new cases of virus transmission between species over the next 50 years, scientists calculate.

This is not a good thing, because according to them, it also increases the risk for humans. More jumping viruses means more chance of encountering them, and more chance of dangerous mutations.

The study simulated how the habitat of more than 3,000 species of mammals would change in a warmer world. Scientists took into account the viruses carried by animals and the degree of relatedness between species – viruses jump more easily between the closest species.

The virus transmission hotspots are mainly places in Africa and Asia with high biodiversity and at higher altitudes. Animal species often migrate to higher and cooler places. If we can limit warming to 2 degrees, the number of contacts between previously unrelated species could double by 2070.

The places where viruses find new hosts are often also densely populated areas, such as parts of Indonesia and India. This increases the risk of a leap from animal to human. “These aren’t just getting warmer, they’re also getting sicker,” says ecologist and study author Gregory Albery (Georgetown University) in Nature†

The protagonists of this story are bats. They are an extremely diverse group – representing around 20% of all mammalian species – and are very capable of carrying viruses without being greatly affected themselves. And as the only flying mammals, they are particularly mobile.

“This study clearly shows how climate change increases the risk of new infectious diseases,” explains virologist Kevin Ariën (Institute of Tropical Medicine). “Although this process is currently taking place mainly in the tropics, it is also impacting us, and it is already in full swing.”