Viruses that originated in bats have overwhelmed humans in past pandemics, and more could be on the way if mutations end up allowing them to spread. An understudied group of coronaviruses known as merbecoviruses contains one viral type of particular concern: HKU5.
A new study published in Nature Communications found that while most merbecoviruses don’t appear likely to impact humans, HKU5 may eventually pose a threat. Bat-borne HKU5 viruses haven't reached humans yet, but all it would take to make the leap is a small mutation that would let them use a host receptor in our bodies, ACE2. Scientists are now keeping a close eye on HKU5, as there’s no telling when it might evolve into a dangerous public health situation.
Bat-Borne Viruses and Humans
One kind of merbecovirus already has a history of infecting humans: the Middle East respiratory syndrome coronavirus (MERS-CoV). Experts identified the first case of MERS in 2012, and it has since led to multiple outbreaks, including a 2015 outbreak in South Korea and a 2018 outbreak in Saudi Arabia. MERS likely originated in bats, but humans are usually infected with the virus through contact with camels.
The story of bats unleashing viruses is a familiar one, yet why are they the animals that often set these deadly events in motion? It turns out that bats are like powder kegs for pandemics due to their unusually robust health. The main factor seems to be their immune system, which has developed to counter many viruses.
As a result, bats can hold onto viruses for long periods without dying, making them the perfect host. Viruses inside them replicate rapidly, and then have a chance of passing to humans, who aren’t nearly as well-equipped to handle them.
Bat-borne viruses often reach humans by way of wildlife trade; one 2025 study suggests that SARS-CoV-2 spread through Asia not by the natural dispersal of its primary host, the horseshoe bat, but by wildlife trade.
Read More: Bat Tolerance to Viral Infections Could Help Humans Become More Resilient, Too
Understanding How HKU5 Spreads
Aside from MERS, the potential impact of merbecoviruses on humans hasn’t been studied extensively in the past, according to a press statement on the new study.
“Merbecoviruses – and HKU5 viruses in particular – really hadn’t been looked at much, but our study shows how these viruses infect cells,” said author Michael Letko, a virologist at Washington State University. “What we also found is HKU5 viruses may be only a small step away from being able to spill over into humans.”
Researchers came to this conclusion after testing the way that merbecoviruses spread, through spike proteins that bind to receptors and infect host cells. They found that HKU5 viruses use the ACE2 host receptor, the same one used by the SARS-CoV-2 virus that causes COVID-19. However, HKU5 viruses can only use the ACE2 gene in bats right now, and they don’t use the human version as effectively.
One Mutation Away From Danger
The concern, though, is that a mutation in the spike protein of HKU5 viruses could allow them to bind to ACE2 receptors in other species, including humans. The natural host for these viruses in Asia is the Japanese house bat, but one HKU5 virus in China has been shown to pass onto minks.
“These viruses are so closely related to MERS, so we have to be concerned if they ever infect humans,” Letko said. “While there’s no evidence they’ve crossed into people yet, the potential is there — and that makes them worth watching.”
The researchers also examined the merbecoviruses using AI, through a program called AlphaFold3. With this program, they were able to model how the HKU5 spike protein connects to ACE2 at a molecular level; this could provide insight into how antibodies react to the viruses or how mutations occur.
The researchers say this study could pave the way for future projects geared toward finding vaccines and treatments, public health measures that could someday become necessary to protect people if HKU5 spreads.
This article is not offering medical advice and should be used for informational purposes only.
Read More: Why Bats Are Breeding Grounds for Deadly Diseases Like Ebola and SARS
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
Nature Communications. ACE2 from Pipistrellus abramus bats is a receptor for HKU5 coronaviruses
University of California- San Diego. Bat Virus Evolution Suggests Wildlife Trade Sparked COVID-19 Virus Emergence in Humans
Jack Knudson is an assistant editor at Discover with a strong interest in environmental science and history. Before joining Discover in 2023, he studied journalism at the Scripps College of Communication at Ohio University and previously interned at Recycling Today magazine.
