Why in the News?

A new study warns that HKU5 bat coronaviruses, closely related to Middle East Respiratory Syndrome coronavirus (MERS-CoV), are just one mutation away from infecting humans.

About HKU5 Virus and Its Characteristics:

• Classification: HKU5 is a bat coronavirus that belongs to the merbecovirus subgenus, which also includes the MERS-CoV (Middle East Respiratory Syndrome coronavirus).
• Origin: It was first identified in the Japanese pipistrelle bat in Hong Kong. “HKU” in the name refers to the University of Hong Kong, where the virus was identified.
• Virology: HKU5 is an enveloped, positive-sense, single-stranded RNA virus, structurally similar to other high-risk coronaviruses.
• Spread: The virus has been detected in bats across Asia, Europe, Africa, and the Middle East, indicating widespread natural reservoirs.
• Cell Entry Mechanism: Like SARS-CoV-2, HKU5 uses the ACE2 receptor to infect cells, but current strains bind effectively only to bat ACE2, not human ACE2.
• Recent Developments: In 2025, a new variant called HKU5-CoV-2 was isolated in China, and lab studies show it can infect human airway and gut cells, though less efficiently than SARS-CoV-2.
• Genetic Similarity: HKU5 is genetically close to both MERS-CoV and SARS-CoV-2, though it has not yet been detected in humans.

Threats and Risks Associated with HKU5 Virus:

• Near-Human Infectivity: HKU5 is considered just one mutation away from gaining the ability to infect humans via the ACE2 receptor.
• Cross-Species Transmission: Certain HKU5 strains have already jumped into minks, demonstrating its capacity to cross species barriers.
• Pandemic Potential: If HKU5 acquires mutations allowing efficient use of human ACE2, it could pose a significant zoonotic pandemic threat.
• Relation to Deadly Viruses: Its structural similarity to MERS-CoV, which has a 34% fatality rate, places HKU5 in a high-risk category if human infection occurs.

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