2 days ago
Overlooked Bat Viruses May Be 'Small Step' From Causing Next Pandemic
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An overlooked subgroup of bat viruses may be just one minor mutation away from being able to infect humans and potentially set off the next pandemic.
This is the warning of a team of U.S.-based researchers who have been studying "merbecoviruses," a coronavirus subgenus that also includes the deadly Middle East Respiratory Syndrome (MERS) virus.
Investigating how these merbecoviruses operate, the scientists found that while most likely pose no direct threat, the "HKU5" subgroup, which can be found across Asia, Africa, Europe and the Middle East, do possess traits that raise concerns.
"Merbecoviruses—and HKU5 viruses in particular—really hadn't been looked at much, but our study shows how these viruses infect cells," said paper author and virologist Michael Letko of the Washington State University in a statement.
"What we also found is HKU5 viruses may be only a small step away from being able to spill over into humans."
Stock image of a Japanese house bat, Pipistrellus abramus, mid-flight
Stock image of a Japanese house bat, Pipistrellus abramus, mid-flight
Russell Jenkins/iStock / Getty Images Plus
Even though thousands of viruses that infect wild animals have had their genomes sequences over the last couple of decades, it is typical that we have little information on the potential risk these agents pose to humans.
And little attention has been given to date to the merbecoviruses, with the notable exception of MERS-CoV.
First detected in 2012, this zoonotic coronavirus—which can be transmitted to us from dromedary camels—causes severe respiratory disease in humans and has a mortality rate of around 34 percent.
Like SARS-CoV-2 (the virus behind COVID-19), merbecoviruses attack host cells by binding to them using a so-called spike protein.
In their study, Letko and colleagues conducted experiments involving virus-like particles that sported only the binding part of the spike, allowing them to study the ability of merbecoviruses to infect human cells.
Although the team found that most merbecoviruses are unlikely to have the capacity to infect humans, the HKU5 subgroup can; in fact, its members latch onto the ACE2 receptor on target cells just like SARS-CoV-2 does.
At present, HKU5 viruses are only able to adequately exploit the ACE2 receptor in bats—and are far less proficient at latching onto those found on human cells.
However, when the researchers analyzed HKU5 viruses from Asia (where their natural host is the Japanese house bat, Pipistrellus abramus), the researchers identified mutations that might allow the viruses to bind to the ACE2 receptors in other species, including humans.
In fact, a study published in 2024 found a HKU5 virus that had spilled over into mink.
"These viruses are so closely related to MERS, so we have to be concerned if they ever infect humans," explained Letko.
"While there's no evidence they've crossed into people yet, the potential is there—and that makes them worth watching."
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References
Catanzaro, N. J., Wu, Z., Fan, C., Jefferson, V., Abdelgadir, A., Schäfer, A., Yount, B. L., Bjorkman, P. J., Baric, R., & Letko, M. (2025). ACE2 from Pipistrellus abramus bats is a receptor for HKU5 coronaviruses. Nature Communications, 16(1), 4932.
Zhao, J., Wan, W., Yu, K., Lemey, P., Pettersson, J. H.-O., Bi, Y., Lu, M., Li, X., Chen, Z., Zheng, M., Yan, G., Dai, J., Li, Y., Haerheng, A., He, N., Tu, C., Suchard, M. A., Holmes, E. C., He, W.-T., & Su, S. (2024). Farmed fur animals harbour viruses with zoonotic spillover potential. Nature, 634(8032), 228–233.
