The ‘super mutant’ Omicron strain of Covid-19 can multiply 70 times faster in the human bronchus than the Delta variant or the original coronavirus, but it results in less severe symptoms, a new study has found.

The ability to multiply at such super-charged speeds might be the reason for Omicron’s faster transmission between humans, researchers at the University of Hong Kong suggested on Wednesday.

“At 24 hours after infection, the Omicron variant replicated around 70 times higher than the Delta variant and the original SARS-CoV-2 virus,” they said after studying lung tissue from patients.

Despite the speed of replication, Omicron replicated 10 times “less efficiently” in the lungs than the original virus, which could point to why the disease appears to be less severe in those which contract the latest variant.

The findings don’t mean the public should not be concerned by Omicron, however. Researchers noted that “by infecting many more people, a very infectious virus may cause more severe disease and death even though the virus itself may be less pathogenic.”

They noted that the severity of disease is also determined by the human host’s immune response to it, adding that in light of other research suggesting Omicron can skirt immunity offered by vaccines and past infection, the overall threat from the variant is still “likely to be very significant.”

The paper from the Hong Kong scientists is currently undergoing peer review for publication.

The emergence of the Omicron variant last month prompted international panic and travel bans, with the World Health Organization (WHO) and medical scientists around the globe suggesting that the new strain could be more contagious and resistant to current vaccines, though it was quickly discovered that the latest variant may not be as harsh as previous ones.