By Will Dunham, Reuters

WASHINGTON — Some of the deadliest diseases to infect humans have come from pathogens that jumped from animals to people. The virus that causes AIDS, for example, crossed over from chimpanzees. Many experts believe the virus that caused the COVID-19 pandemic flowed from bats.

But, as a new study shows, this exchange has not been a one-way street. An analysis of viral genome sequences yielded a surprising result: Humans give more viruses — about twice as many — to animals than they give to us.

The researchers looked at nearly 12 million virus genomes and detected almost 3,000 instances of viruses jumping from one species to another. Of those, 79% involved a virus going from one animal species to another animal species. The remaining 21% involved humans. Of those, 64% were human-to-animal transmissions, known as anthroponosis, and 36% were animal-to-human transmissions, called zoonosis.

The animals affected by anthroponosis included pets such as cats and dogs, 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 black-tufted marmoset and the African soft-furred mouse.

'No pre-existing immunity'

Over the millennia, pandemics that have killed millions of people have been caused by pathogens such as viruses, bacteria and fungi that crossed over to people from animals. Zoonosis has been the primary concern concerning dangerous emerging infectious diseases.

"The vast majority of pathogens circulating in humans have been acquired from animals at some point in time," said computational biologist and study co-author Francois Balloux, director of the UCL Genetics Institute.

"The current biggest threat is probably bird flu H5N1, which is circulating in wild birds. The main reason recent host jumps can be so devastating is because the population of host species has no pre-existing immunity to the novel disease," Balloux added.

The 14th century Black Death — when the bacterial disease bubonic plague killed millions of people in Europe, Asia, the Middle East and North Africa — was caused by a bacterium normally circulating in wild rodents.

https://www.ksl.com/article/50962446/humans-give-more-viruses-to-animals-than-they-give-us-study-finds