"Unusual Habit: Human Hosts as Frequent Jumping Grounds"

In a groundbreaking study published in Nature Ecology & Evolution, scientists have challenged the prevailing notion that viral host jumps predominantly originate from animals and move to humans. The research, conducted by Tan et al., delves into the evolutionary mechanisms that underlie these zoonotic (animal-to-human) and anthroponotic (human-to-animal) transmissions.

The team analyzed genetic evolution patterns in viruses associated with zoonotic and anthroponotic host jumps, using an extensive dataset of viral genomic data. Their findings reveal that humans are as much a source of viral spillover events to other animals as they are recipients.

To address the challenge of non-uniform viral taxonomy, the researchers developed an automated protocol that constructed closely related 'viral cliques' as operational taxonomic units. This grouped together different viral species into single cliques and, in other cases, split a single species into distinct cliques. The resulting 5,128 cliques served as a standardized framework for categorizing viruses on the basis of genetic similarity rather than relying on traditional - often inconsistent - taxonomy.

The authors inferred phylogenies for all viral cliques and studied the changes that happened on these 'host jump' branches. Although most viral cliques showed no jumps, some revealed frequent jumps to new hosts. Interestingly, viral host jumps from humans to animals tended to occur almost twice as frequently as the other way around.

The study also found that certain viruses have advantageous mutations to infect new hosts and are thus predisposed to jumping between hosts. However, the authors acknowledge the limitations of their research, including the sampling bias inherent in the dataset and the need for more systematic and uniform data collection practices.

The findings of this study provide interesting insights into the complex dynamics of viral host jumps but also underscore the need for more systematic genomic surveillance and a collaborative global health framework that transcends species and geographical boundaries. By integrating comprehensive viral genomic data with ecological and environmental insights, we might get better at predicting, preventing and mitigating viral spillovers.

Source: <https://www.nature.com/articles/s41559-024-02377-w>