Washington. Some of the deadliest diseases that have plagued humanity come from pathogens that jumped from animals to people. The virus that causes AIDS, for example, passed from chimpanzees. And many experts believe that the virus that caused the Covid-19 pandemic came from bats.
But, as a new study shows, this exchange has not been one-way. An analysis of all publicly available viral genome sequences yielded a surprising result: humans transmit more viruses – approximately twice as many – to animals than they transmit to us.
The researchers analyzed almost 12 million virus genomes and detected almost 3 thousand cases of viruses that jumped from one species to another. Of them, 79 percent were viruses that passed from one animal species to another. The remaining 21 percent concerned humans. Of those, 64 percent were human-to-animal transmissions, known as anthroponoses, and 36 percent were animal-to-human transmissions, known as zoonoses.
Among the animals affected by anthroponosis were domestic animals such as dogs and cats, domesticated animals such as pigs, horses and cattle, birds such as chickens and ducks, primates such as chimpanzees, gorillas and howler monkeys, and other wild animals such as raccoons, the marmoset black tufted mouse and the African soft-haired mouse.
In particular, wild animals were much more likely to transmit between humans than the other way around.
“This highlights our enormous impact on the environment and the animals around us,” says Cedric Tan, a PhD student in computational biology at the Institute of Genetics at University College London and lead author of the study published this week in the magazine Nature Ecology & Evolution.
People and animals are hosts to countless microbes that can jump to another species through close contact. The study analyzed viral transmissions that affect all groups of vertebrates: mammals, birds, reptiles, amphibians and fish.
“Viruses can jump from one species to another through the same modes of transmission that apply to humans, such as direct contact with infected fluids or bites from other species, among others,” explains Tan.
“However, before a virus can jump to a new host, it must already possess the biological toolkit, or acquire host-specific adaptations, to enter the cells of the new host species and exploit its resources,” Tan added. .
Over the millennia, pandemics that have killed millions of people have been caused by pathogens such as viruses, bacteria and fungi that jumped from animals to people. Zoonoses have been the main concern regarding dangerous emerging infectious diseases.
“The vast majority of pathogens circulating among humans have been acquired from animals at some point,” says computational biologist and study co-author Francois Balloux, director of the UCL Institute of Genetics.
“The biggest current threat is probably H5N1 avian flu, which circulates in wild birds. The main reason why the recent host jumps can be so devastating is because the host species population has no pre-existing immunity to the new disease,” Balloux added.
The Black Death of the 14th century – when the bacterial disease bubonic plague killed millions of people in Europe, Asia, the Middle East and North Africa – was caused by a bacteria that normally circulated in wild rodents.
And current threats like the Ebola virus also emerged from animals.
“It is widely believed that SARS-CoV-2, the agent of the Covid-19 pandemic, likely originated in horseshoe bats and jumped to humans,” Tan said.
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– 2024-04-06 14:43:01
