Five years after SARS-CoV-2 triggered a worldwide pandemic, leading to widespread devastation, another bat-borne coronavirus HKU5-CoV-2 - a distant cousin of Covid-19 has been discovered in China’s Wuhan Institute of Virology. It has caused concern as the new bat coronavirus is capable of binding to the ACE2 reception in human cells, the same pathway, the Covid-19 virus used to infect humans.

HKU5-CoV-2, belonging to the merbecovirus subgenus , includes the MERS virus . The findings of the study published in the journal Cell found that HKU5-CoV-2 could infect human cells in laboratory settings and highlighted its potential to jump species. It can also bind to ACE2 receptors in a variety of mammals, which means multiple intermediate hosts could facilitate its transmission to humans.

Researchers collected the HKU5-CoV-2 strain from a small subset of hundreds of Pipistrellus bats swabbed across China’s Guangdong, Fujian, Zhejiang, Anhui, and Guangxi provinces. The research was led by virologist Shi Zheng-Li, known for her work on bat viruses. Her facility had faced allegations about its central role in the emergence of SARS-CoV-2.

HKU5-CoV-2 is part of the merbecovirus subgenus, which also includes the Middle East respiratory syndrome (MERS) virus. It was initially detected in the Japanese pipistrelle bat species in Hong Kong. Researchers have found that this virus can bind to angiotensin-converting enzyme 2 (ACE2) receptors, the same cellular receptors used by SARS-CoV-2 to infect human cells. Additionally, HKU5-CoV-2 has been observed to attach to ACE2 receptors in various mammalian species, raising concerns about cross-species transmission .

Can HKU5-CoV-2 cause an outbreak?"Although HKU5-CoV-2 utilizes ACE2 receptors like SARS-CoV-2, its ability to bind to human cells is significantly weaker. Laboratory tests indicate that while the virus can infect human lung tissue, it lacks the efficiency needed for widespread human transmission. This reduced infectivity minimizes the immediate risk of an outbreak," says Dr Tushar Tayal, Consultant, Internal Medicine, CK Birla Hospital, Gurugram.

No major public threatScientists caution against alarm, stating that while the virus can enter human cells in lab conditions, there is no evidence suggesting it could easily spread among humans.

"Unlike SARS and MERS, which demonstrated efficient human-to-human transmission, HKU5-CoV-2 does not currently pose a major public health threat ," says Dr Tayal.

Difference between SARS-CoV-2 and HKU5-CoV-2

SARS-CoV-2Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is the causative virus for COVID-19, which initiated the pandemic in late 2019 globally. It is a betacoronavirus genus and Sarbecovirus subgenus. SARS-CoV-2 causes moderate influenza-like disease to severe pneumonia and multi-organ failure and is primarily spread by respiratory droplets and direct contact. It has undergone numerous mutations, giving rise to variations with differing degrees of transmissibility and immunological evasion, including Alpha, Delta, and Omicron.

HKU5-CoV-2HKU5-CoV-2 is a bat coronavirus initially found in Rousettus bats in Hong Kong. HKU5-CoV-2 is a member of the Merbecovirus subgenus of betacoronaviruses and is therefore genetically different from SARS-CoV-2. HKU5 is not a human pathogen, but studies were conducted on its ability to cross species boundaries. Although SARS-CoV-2 led to a pandemic, scientists remain interested in HKU5, particularly with regard to coronavirus evolution and the potential for zoonotic spillover.

"SARS-CoV-2 and HKU5-CoV-2 differ in several significant respects. HKU5-CoV-2 belongs to the Merbecovirus subgenus, while SARS-CoV-2 belongs to the Sarbecovirus subgenus.

"Their host origins are also different; HKU5-CoV-2 is mainly hosted by bats, whereas SARS-CoV-2 is believed to have originated in bats with a possible intermediary host such as pangolins," says Dr Rituja Ugalmugle, Internal Medicine, Wockhardt Hospitals, Mumbai Central.

Dr Ugalmugle says while HKU5-CoV-2 has not been found to infect humans, SARS-CoV-2 has led to extensive human-to-human infection, leading to a global health crisis.

The expert notes that while SARS-CoV-2 led to a pandemic across the world, HKU5-CoV-2 is under investigation and has not been associated with any severe public health concerns.

"Though both are coronaviruses, HKU5-CoV-2 is not human-pathogenic as SARS-CoV-2, but its study is included in pandemic preparedness and coronavirus evolution," added Dr Ugalmugle.