It’s not uncommon for cats to bring home “spoils” from their hunt — usually a mouse, lizard, or some other unlucky creature. So, it wasn’t a shock when Pepper, a Florida cat, came back with a cotton mouse (Peromyscus gossypinus). But Pepper’s owner, John Lednicky, is a microbiologist and virus hunter at the University of Florida. So rather than toss out the rodent, Lednicky brought it to his lab. And there, he made an unexpected discovery: a previously unknown virus.

A new virus

Lednicky and his team initially tested the mouse to see if it carried mule deerpox virus (MDPV), a pathogen that has recently spread through Florida and a few other US states. Instead, they discovered something completely new.

By using next-generation sequencing technology, the researchers decoded the virus’ genome and classified it within the paramyxovirus lineage.

Paramyxoviruses belong to a larger group called Jeilongviruses. This family includes viruses responsible for measles and mumps in humans, as well as severe animal diseases like Hendra and Nipah. The newly identified virus, named GRJV1, exhibited an ability to infect various mammalian cell types, from rodents to humans. This broad “cell tropism” suggests the virus could potentially spill over from animals to humans or other mammals, which raises some concerns.

An adaptable pathogen

To explore how widely GRJV1 could infect different cells, the researchers ran tests on cultures from various animal cells, including monkey lung and kidney cells, human liver cells, and mouse brain cells. GRJV1 not only infected all these cell types but also damaged them, causing changes like cellular fusion — a common result of viral infections.

Using a technique called plaque assay, they measured the virus’s growth rates and found it replicated most efficiently in human and primate cells, with rodent cells not far behind. This adaptability points to an evolution that enables the virus to latch onto and replicate in diverse species, possibly using multiple cell receptors.

Traditionally, Jeilongviruses were thought to infect only small mammals. But recent discoveries, including viruses in bats and other animals, reveal a broader evolutionary spread. Jeilongviruses have RNA genomes and are known for their ability to jump between species. This makes them a focus of zoonotic research (a zoonotic disease is one that jumps from animals to humans). Their versatility may relate to their structure, which potentially enables them to infect various hosts, posing potential health risks for humans and animals alike.

However, as humans are also primates, this raises an important question.

Does the virus pose a threat to humans?

Viral spillover events, where a virus jumps from one species to another, can be devastating. Fortunately, these events are rare. Even if GRJV1 could infect humans, it’s unlikely that it would transmit easily from person to person. Still, caution is warranted, and more research is needed to monitor this virus closely and understand its risks.

In this case, we don’t know how serious the risk of spillover is. We don’t know how widespread the virus is. We don’t even know what kind of a disease it could cause in humans. After all, infecting cells in the lab is not the same as infecting an organism.

The risk the virus poses to humans is, most likely, very low. But with a virus like GRJV1, which demonstrates a broad host range, there is an urgent need for improved surveillance.

The problem is that the funding for this type of research is almost non-existent.

This shows, once again, how much we need virus surveillance

For decades, researchers have warned that we need monitoring in wildlife populations where potential zoonotic agents, animals, and humans frequently intersect. Early detection and identification of zoonotic viruses circulating within rodent and bat populations could be instrumental in preventing outbreaks, particularly in densely populated urban settings.

As urban development encroaches into wildlife habitats, contact with rodent species and their potential viral passengers becomes more likely. Furthermore, the increasingly globalized movement of people and goods increases the likelihood that new viruses can travel far beyond their points of origin, making monitoring all the more complicated.

But there’s little funding for surveillance research of this nature, Lednicky told Gizmodo. The work is expensive, requiring trained personnel and specialized equipment. The funding for such surveillance projects it not nearly enough — even though it would be a good investment.

The threat from this particular virus may be small, but its discovery underscores the ever-present and evolving threat posed by zoonotic diseases. We’ve seen in the COVID-19 pandemic that all it takes is one virus to cause immeasurable cost to human society.

As for Pepper, he was left completely unharmed by his meeting with the virus-carrying rodent. Every now and then, Pepper will still bring home some hunting spoils, carrying who-knows-what viruses.

The study “A Novel Jeilongvirus from Florida, USA, Has a Broad Host Cell Tropism Including Human and Non-Human Primate Cells” was published in the journal Pathogens.