We transmit more viruses to animals than we think

We transmit more viruses to animals than we think

Chikungunya, echinococcosis, avian flu… Animals can transmit many diseases to us. But the opposite is just as true. An English study shows that we too can make our animal friends sick.

Researchers from University College London made this discovery after analyzing nearly twelve million viral sequences deposited in public databases. They were thus able to reconstruct the trajectories where the viruses jumped from one host to another to infect another species of vertebrates, within the framework of around thirty viral families.

Because human health is closely linked to that of wildlife and ecosystems. Viruses, bacteria and parasites take many twists and turns before infecting our species, and therefore becoming what we commonly call zoonoses. When these pathogens cross the barrier between animals and humans, they can trigger epidemics and even pandemics, as was the case with Covid-19 (SARS-CoV-2).

Until now, it was thought that zoonotic transmission was to the detriment of humans, who would be more of a sink for pathogens rather than a reservoir. But the authors of this research found that humans frequently spread viruses to wild, farmed and domestic animals. In detail, they identified twice as many infections from humans to animals than the reverse.

Prevent possible pandemics?

This highlights the tremendous impact we humans have on the animals around us. “When animals catch human-transmitted viruses, it can not only harm the animal and pose a potential threat to the conservation of the species, but also cause new problems for humans by impacting the food safety if large numbers of livestock need to be slaughtered to prevent an outbreak, as has happened in recent years with the H5N1 strain of avian flu“, explains Cedric Tan, molecular biologist at University College London and first author of the study, in a press release.

This phenomenon is all the more worrying because with each change of host, from one species to another, the viral genomes modify to better adapt to their new host. “If a virus carried by humans infects a new animal species, it can continue to develop even if it is eradicated in humans, or even develop new adaptations before infecting humans again,” emphasizes Cedric Tan.

Cedric Tan and his colleagues hope that their study, published in the journal Nature Ecology & Evolution, will encourage more research on the impact of viruses transmitted by humans on wildlife to reduce zoonotic risk. “By monitoring and controlling the transmission of viruses between animals and humans, in both directions, we can better understand viral evolution and, hopefully, be better prepared for future outbreaks and epidemics of new diseases, while contributing to conservation efforts,” says Professor François Balloux, director of the Genetics Institute at University College London, in the same press release.

With the hope that this will allow us to anticipate emerging infections, before one of them degenerates into a pandemic.