Researchers say that compared to the earlier Delta variant, Omicron multiplies itself 70 times more quickly in tissues that line airway passages, which may facilitate person-to-person spread. But in lung tissues, Omicron replicates 10 times more slowly than the original version of the coronavirus, which might contribute to less-severe illness.

A formal report of the findings is under peer review for publication and has not been released by the research team. In a news release issued by Hong Kong University, study leader 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 each person's immune response to the infection, which sometimes evolves into life-threatening inflammation.

Chan added, "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 Omicron variant is likely to be very significant."

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