The Omicron variant multiplies 70 times faster than Delta in human airways, according to researchers.
The study also suggested that Omicron replicates less well in human lung tissue compared with the original strain of the virus
Researchers said this could indicate a lower severity of disease.
What the study found on the Omicron variant
However, the study’s lead professor warned that the “overall threat from the Omicron variant is likely to be very significant”.
Dr Michael Chan Chi-wai said it is important to note “that the severity of disease in humans is not determined only by virus replication but also by the host immune response to the infection”.
The associate professor, at the school of public health at LKS Faculty of Medicine at The University of Hong Kong (HKUMed), added: “It is also 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.
“Therefore, taken together with our recent studies showing that the Omicron variant can partially escape immunity from vaccines and past infection, the overall threat from the Omicron variant is likely to be very significant.”
How researchers made the discovery about the Omicron variant
Researchers who carried out the study said their work provides the first information on how the new variant infects people.
They said that they had successfully isolated the Omicron variant and used lung tissue removed for treatment of the lung, to investigate the new mutation.
They compared Omicron with the original strain, and with Delta.
Omicron multiplies 70 times faster than Delta in human airways
A release, published by HKUMed, said they found that Omicron “replicates faster than the original Sars-CoV-2 virus and Delta variant in the human bronchus”.
They said that 24 hours after infection, the Omicron variant “replicated around 70 times higher than the Delta variant and the original Sars-CoV-2 virus”.
They added: “In contrast, the Omicron variant replicated less efficiently (more than 10 times lower) in the human lung tissue than the original Sars-CoV-2 virus, which may suggest lower severity of disease.”
The research is currently under peer review for publication, the university said.
Reaction to the Omicron study
Reacting to the university’s release on the study, Dr David Strain, senior clinical lecturer at the University of Exeter, said it is unclear how the results of this laboratory-based work will compare to what is seen in patients.
He said: “The 70-fold increase in replication is of concern which does account for the increased transmissibility of the virus.
“There is a lack of clarity however, as to how this 10-fold reduction in lung infectivity in this lab-based study will translate in patients.
“At first glance it looks good news, however if the virus can replicate 70 times quicker, but infects 10 times slower, that still results in a seven-fold increased risk of disease (70 times more virus, even with a 10-fold reduction in ability to enter the cells will cause the virus to overwhelm the cells).”
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