In the intricate web of life, the flow of viruses between species is more complex than previously believed. Recent research has revealed a surprising dynamic: humans are more often the source of viruses for animals than the other way around.

This finding challenges long-standing assumptions and highlights the need for a broader perspective on our role in the transmission of infectious diseases.

Photo: Pexels
Humans transmit more viruses to animals than vice versa.

Unraveling the Flow of Viruses

An extensive study published in Nature Ecology & Evolution, analyzing nearly 12 million viral genomes, has uncovered that human-to-animal transmissions, termed anthroponosis, occur at nearly double the rate of animal-to-human transmissions, known as zoonosis.

The research, spanning all vertebrate groups, found that 64% of interspecies viral transmissions involving humans were from us to animals. As Reuters reports, the affected animals include pets, livestock, and various wild species.

This phenomenon has significant implications for both animal conservation and human health.

Photo: Pexels
A study analyzed nearly 12 million viral genomes across various species.

As Cedric Tan, a doctoral student at the University College London Genetics Institute and lead author of the study, noted such transmissions can threaten animal populations and, by extension, impact human food security.

"Viruses can jump between different species via the same modes of transmission that apply to humans, including direct contact with infected fluids, or getting bitten by other species, amongst others," Tan said.

"However, before a virus can jump into a new host, it must either already possess the biological toolkit, or acquire host-specific adaptations, to enter the cells of the new host species and exploit their resources," he added.

Photo: Pexels
Human-to-animal virus transmission is known as anthroponosis.

The Evolutionary Dynamics Behind Viral Jumps

The study delves into the evolutionary mechanisms driving these transmissions. Viruses that successfully jump between species often exhibit heightened evolution, particularly in viral lineages involving host jumps.

Surprisingly, viruses with broader host ranges show lower adaptation requirements for successful jumps, suggesting an innate capability to infect diverse hosts without significant genetic changes.

Furthermore, the study found that the genomic targets of natural selection, essential for a virus to adapt to a new host, vary among viral families, the University of Minnesota reports. This variability underscores the complexity of viral evolution and the myriad factors influencing the success of interspecies transmission.

Photo: Pexels
Rethinking our interactions with animals is essential to prevent unintended viral transmissions.

Rethinking Our Place in the Viral Ecosystem

As The Independent reports, this research challenges the traditional view of humans as mere recipients of animal viruses. Rather, it positions us as active participants in a vast network of viral exchange.

Professor Francois Balloux, a co-author of the study, advocates for a broader perspective that considers humans as one node in a network of hosts, endlessly exchanging pathogens.

“We should consider humans just as one node in a vast network of hosts endlessly exchanging pathogens, rather than a sink for zoonotic bugs," Balloux said. “By surveying and monitoring transmission of viruses between animals and humans, in either direction, we can better understand viral evolution and hopefully be more prepared for future outbreaks and epidemics of novel illnesses, while also aiding conservation efforts.”

This shift in perspective is crucial for understanding viral evolution and preparing for future outbreaks. By monitoring viral transmissions in both directions—animal to human and human to animal—we can gain insights into the emergence of new diseases and inform conservation efforts.

Photo: Pexels
The research challenges the traditional view of humans as mere recipients of animal viruses.

Implications for the Future

The study's findings highlight the need for more comprehensive surveillance of viral diseases, encompassing the full spectrum of host species. This broader approach could enhance our understanding of viral ecology and evolution, informing strategies to mitigate the impact of infectious diseases on human health and biodiversity.

This research illuminates the complex interplay between humans and animals in the realm of infectious diseases. By recognizing our role in transmitting viruses to animals, we can adopt more holistic approaches to disease surveillance and management, ultimately safeguarding both animal populations and human communities.