According to tissue samples obtained from the bronchus, the primary tubes connecting the windpipe to the lungs, the Omicron variant was shown to proliferate 70 times faster than the original COVID-19 and Delta variants. 

Hong Kong researchers also discovered that the Omicron variant expands 10 times slower in lung tissue, which could indicate reduced severity of the disease.

According to Michael Chan Chi-wai, the head of the experiment, the severity of the disease cannot only be determined by how fast the disease replicates, but how the immune system responds.

He added 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.”

According to Jeremy Kamil, an associate professor of microbiology and immunology at Louisiana State University, the Delta variant replicates at a slower rhythm in the lungs.

“Of course, a huge component of Omicron’s transmissibility in real life is going to be its potential to escape neutralizing antibodies that protect against infection in the first place. It’s very likely spreading well even between vaccinated people, especially those who haven’t recently gotten a booster shot," he said.

The original findings were found using lung tissue samples from patients undergoing surgery. After 24 hours, Omicron had replicated 70 times quicker than the original infection and the Delta variant. Despite the fact that the bronchus is not part of the upper respiratory system, experts believe that this might result in people shedding more viruses and becoming more contagious.