New virus discovered in China is ‘small step’ away from triggering a pandemic

Nearly five years after the start of the COVID-19 pandemic, scientists have identified another coronavirus with the potential to cross into humans—and this time, they’re sounding the alarm early. The virus, named HKU5-CoV-2, was discovered in bat populations in China and is closely related to MERS-CoV, a deadly virus that kills roughly one-third of those it infects. According to a recent study led by virologists at Washington State University, HKU5-CoV-2 may be only a few mutations away from gaining the ability to infect human cells. While no human cases have been reported to date, the findings underscore how quickly a seemingly obscure animal virus can evolve into a global health threat.

The warning comes at a critical juncture, as global health systems remain strained and pandemic fatigue has dulled public sensitivity to emerging threats. But the science behind HKU5-CoV-2 offers a clear and timely lesson: zoonotic viruses—those that jump from animals to humans—are not rare anomalies, but recurring biological events, often enabled by human activity. Understanding the mechanisms that allow these viruses to adapt, and the environmental conditions that promote spillover, is essential to preventing the next crisis.

A Virus on the Brink — What Makes HKU5-CoV-2 a Pandemic Threat

A newly identified coronavirus in China, HKU5-CoV-2, is drawing concern from scientists for its close genetic relationship to MERS-CoV—the virus responsible for Middle East Respiratory Syndrome, which has a fatality rate of approximately 34%. Researchers from Washington State University warn that HKU5-CoV-2 may be only a minor mutation away from gaining the ability to infect humans, raising the specter of another potential pandemic. Originally discovered in 2005 in Japanese house bats (Pipistrellus abramus), the virus was not previously thought to pose a serious threat. However, recent findings using live virus testing, AI simulations, and protein modeling have shown that its spike protein structure can bind readily to bat ACE2 receptors and may adapt to human receptors with relative ease.

In the study published in Nature Communications, scientists created lab-engineered pseudoviruses—harmless particles designed to mimic viral behavior—and introduced them to both bat and human cells. The HKU5 virus lit up brightly in bat cells, confirming its natural infectivity in its original host. Human cells, on the other hand, remained largely unaffected unless the virus’s spike protein was modified to mimic specific mutations, at which point it began to successfully enter human cells via ACE2 receptors—the same cellular entry point exploited by SARS-CoV-2. Alarmingly, one strain of HKU5, known as Lineage 2, already appears capable of binding to human ACE2 without further mutation, suggesting that at least part of the virus family may already be “pre-adapted” for human infection.

What makes HKU5-CoV-2 particularly concerning is the potential for it to evolve further through intermediate animal hosts such as mink or civets—species known from past outbreaks to act as bridges between bats and humans. The virus’s spike protein remains in a relatively “closed” configuration, making infection more difficult but not impossible. If it circulates widely among susceptible animal populations, it could acquire key mutations that would allow it to efficiently infect humans, just as

zoonotic viruses have done. The unregulated wildlife trade and high-density animal markets further exacerbate the risk, creating ideal conditions for such cross-species transmission events.

While there is currently no evidence that HKU5-CoV-2 has infected humans, experts emphasize the importance of proactive surveillance and global preparedness. Dr. Michael Letko, who co-led the study, cautions that although HKU5 viruses have not yet crossed over, the potential is clearly present. Considering the virus’s genetic proximity to MERS and its emerging ability to bind to human cells, HKU5-CoV-2 represents a significant biological threat that warrants serious attention before the “small step” toward human transmission becomes a leap.

How Scientists Are Studying the Threat — Inside the Research

To assess the potential risk posed by HKU5-CoV-2, researchers employed a multi-pronged approach combining laboratory virology, protein imaging, and artificial intelligence modeling. These advanced methods allowed them to examine how the virus interacts with host cells, particularly focusing on the spike protein, which plays a critical role in viral entry. Using gene-editing tools, the scientists engineered pseudoviruses—non-replicating viral particles fitted with the HKU5 spike protein—to observe whether they could penetrate cells expressing either bat or human ACE2 receptors. The results were telling: while bat cells were easily infected, human cells remained mostly resistant unless the pseudovirus contained specific mutations that enhanced its binding affinity to human receptors. This experiment underscored just how close the virus may be to acquiring the ability to infect humans through naturally occurring evolutionary shifts.

One of the standout aspects of the study was the use of cryo-electron microscopy, a high-resolution imaging technique that allowed the team to visualize the structural conformation of the virus’s spike protein. What they found was that HKU5’s spike typically remains in a “closed” state—an arrangement that makes it harder for the virus to initiate infection. However, this structure is not fixed. Small structural changes could potentially “open” the spike protein, exposing the binding sites needed to attach more efficiently to human ACE2 receptors. These changes are the kind that can emerge as the virus adapts to new hosts, especially when circulating among animals that can serve as intermediaries, such as civets or camels, as was the case with SARS and MERS respectively.

The study also expanded its scope beyond a single strain, examining a wide range of merbecoviruses to identify others that might pose similar threats. By analyzing dozens of HKU5 variants along with known strains of MERS-CoV, the researchers aimed to build a broader picture of which viral lineages are most likely to spill over into humans. Their findings revealed that while HKU5 Lineage 2 may already be primed for human infection, several other variants are only a few mutations away. This insight not only raises the alarm about HKU5-CoV-2 but also signals a broader risk across this underexamined family of viruses.

The Role of Wildlife Trade and Human-Animal Interfaces

One of the most pressing concerns highlighted by the HKU5-CoV-2 discovery is the ongoing risk posed by unregulated wildlife trade and the close interactions between humans and wild animals. Although HKU5-CoV-2 is currently confined to bat populations, the potential for it to mutate and adapt increases significantly if it passes through one or more intermediate animal hosts. Historical precedents like SARS, which likely jumped from bats to civets before infecting humans, and MERS, which spread from camels, illustrate how these zoonotic spillover events often occur in environments where wild and domestic animals are kept in close quarters under stressful, unsanitary conditions. These situations not only encourage viral adaptation but also facilitate direct exposure to humans—especially in live animal markets where species that would never naturally interact are housed together.

Researchers collected the HKU5-CoV-2 strain from bats in southern and eastern China, regions known for high biodiversity and frequent human-animal contact. These areas also have active wildlife markets and limited regulation, creating ideal conditions for cross-species viral transmission. In such settings, viruses like HKU5 can circulate undetected among animals and quietly accumulate mutations. If one of these mutations enhances the virus’s ability to bind to human ACE2 receptors—as the Washington State University team has shown is possible—the risk of human infection becomes immediate. The danger is not merely theoretical; it is a practical consequence of systemic gaps in wildlife management and public health surveillance.

While much of the global attention has focused on high-profile outbreaks once they’ve already occurred, experts argue that preventing pandemics begins with minimizing the opportunity for these spillovers in the first place. This involves stricter oversight of the wildlife trade, improved conditions for animals in wet markets, and better education for communities that rely on bushmeat or live animal commerce. According to virologists, many of the most threatening viruses share similar pathways into the human population—through contact with stressed, infected animals in compromised environments. Yet, despite the well-documented risks, enforcement remains uneven and underfunded, particularly in regions where these markets serve as important economic or cultural centers.

Lessons from COVID-19 and MERS — Why Early Warning Matters

The emergence of HKU5-CoV-2 is particularly unsettling in light of the hard-earned lessons from recent coronavirus outbreaks, especially COVID-19 and MERS. Both viruses originated in animals, spilled over into humans through intermediate hosts, and caught the world off guard with their speed and severity. COVID-19, which is believed by several U.S. intelligence agencies including the FBI and CIA to have likely originated from a lab leak or animal spillover at the Wuhan Institute of Virology, demonstrated how delayed response and limited transparency can fuel a global crisis. In contrast, MERS—which first emerged in Saudi Arabia in 2012 and is transmitted from camels—remains regionally contained but has a far higher mortality rate, killing roughly one in three people it infects. What links these viruses is not just their biological similarities, but also the missed opportunities for earlier intervention.

HKU5-CoV-2, being closely related to MERS-CoV and now shown to have at least one lineage that can bind to human ACE2 receptors, fits into a troubling pattern: novel viruses with known pandemic potential being identified only after they’ve begun circulating among animals for years. The fact that HKU5 was first discovered in 2005 but only recently examined for its human infection potential highlights a gap in long-term virological surveillance. As Dr. Michael Letko and his team’s research reveals, some variants within the HKU5 family may already possess the molecular tools needed to infect people. This is not just a theoretical warning—it’s a biological possibility backed by live experiments and structural analysis.

Global health agencies have repeatedly called for early detection systems to identify and track viruses before they emerge in human populations. Yet, in practice, surveillance has been fragmented and underfunded. COVID-19 exposed the consequences of such systemic vulnerabilities—overwhelmed healthcare systems, supply chain disruptions, and enormous social and economic tolls. With HKU5-CoV-2, the scientific community has the advantage of foresight. Virologists have already mapped its spike protein, tested its infectivity, and warned about the conditions under which it could adapt to humans. The question now is whether those in charge of pandemic preparedness will act on this information, or once again wait until the virus has already made the leap.

Understanding these early warnings is critical not just for scientists, but for governments, public health agencies, and the broader public. Pandemics rarely appear out of nowhere—they develop over time, often in plain sight. The current findings on HKU5-CoV-2 offer an opportunity to do better, to heed the signals, and to address the risks before another virus catches the world unprepared. Prevention may be less dramatic than crisis response, but it is undeniably more humane, cost-effective, and ultimately lifesaving.

From Awareness to Action — What Needs to Happen Now

The discovery of HKU5-CoV-2 is not merely a scientific revelation; it’s a call to action. With the virus showing the potential to infect human cells after just minor mutations, the window for meaningful prevention remains open—but it won’t stay that way indefinitely. Experts agree that pandemic preparedness must extend beyond reactive containment strategies to proactive surveillance, cross-border cooperation, and investment in virus-tracking infrastructure, particularly in regions with high biodiversity and dense human-animal contact. Early detection tools, such as genetic sequencing and real-time monitoring of zoonotic viruses, need to be scaled and integrated into global health systems—not just for HKU5, but for the many other under-researched pathogens lurking in wildlife populations.

One of the clearest imperatives is stricter oversight of wildlife markets and the global wildlife trade. Despite repeated warnings, many such markets continue to operate with minimal regulation, creating perfect environments for viral spillover. Enforcement of sanitary standards, reduction of live animal trade, and public education on zoonotic risks are critical steps that must be taken in tandem with scientific research. International agencies, including the World Health Organization and the World Organisation for Animal Health, should work with national governments to build policies that prioritize ecological health as a pillar of human health. The “One Health” framework—an interdisciplinary approach recognizing the interconnectedness of human, animal, and environmental health—is more relevant than ever.

Public communication also plays a central role. Fear-based messaging can lead to stigma and misinformation, but clear, transparent communication grounded in evidence can build public trust and drive informed action. The case of HKU5-CoV-2 should not be framed as a guaranteed disaster, but rather as a credible and avoidable risk—one that highlights the value of listening to science before crisis hits. As COVID-19 demonstrated, delayed action can come at an enormous human and economic cost. Learning from past failures means institutionalizing the mechanisms that ensure scientists’ warnings don’t go unheeded.

Ultimately, the message from virologists is not one of alarmism but urgency. We are not powerless against the next potential pandemic. The knowledge we have today about HKU5-CoV-2—its structure, behavior, and potential pathways into human populations—gives us a rare advantage. It is up to policymakers, health leaders, and civil societies to translate that knowledge into swift, coordinated action. We’ve seen what happens when we wait. This time, we don’t have to.