The Omicron Covid variant has been found to be 70 times more likely to spread than the original and Delta versions of coronaviruses in tissue samples taken from the bronchus, the main tubes from the windpipe to the lungs.
The new variant grew 10 times slower in lung tissue than the old variant, which the authors said could be an indicator of lower disease severity.
Michael Chan Chi-wai, who led the work, said the result needed to be interpreted with caution because severe disease is determined by how quickly the virus replicates and by a person's immune response.
He said that a very infectious virus may cause more severe disease and death even if it is less harmful. The threat from the Omicron variant is likely to be very significant, because of the fact that it can partially escape immunity from vaccines and past infections.
The pattern of replicating in the lungs was similar to that of Delta, which was more pathogenic, according to Jeremy.
The authors found that Omicron was even better than Delta or the original virus in replicating in bronchial tissue. This could contribute to an advantage in the transmission of information.
Omicron has the potential to escape neutralising antibodies that protect against infections in the first place. It is likely to spread even between people who have not recently gotten a booster shot.
The data came from experiments using lung tissue samples taken from patients during surgery. The Omicron variant replicated 70 times more than Delta and the original variant. The bronchus isn't the upper respiratory system, so it could lead to people getting more infections.
Recent work shows that the variant may be more transmissible in addition to evading immunity.
