Omicron variant found to grow 70 times faster than Delta in respiratory tissue

University of Hong Kong study says COVID-19 mutation multiplies rapidly in bronchus, but much more slowly in the lungs compared to initial coronavirus; is possibly less severe

An image produced by US researchers shows SARS-CoV-2 virus particles (red), covering human bronchial cilia (blue), and mucus (yellow). (Ehre Lab, UNC School of Medicine)
Illustrative: An image shows COVID-19 virus particles (red), covering human bronchial cilia (blue), and mucus (yellow) Image does not show Omicron variant. (Ehre Lab, UNC School of Medicine)

The Omicron variant of COVID-19 has been found to multiply about 70 times faster in bronchial tissue than the Delta mutation or the original coronavirus strain, a study has shown.

A team from the University of Hong Kong saw the rampant reproduction in tissue samples taken from the lower respiratory passage of patients undergoing surgery.

In a 24-hour period, Omicron was found to replicate about 70 times faster than Delta. Researchers said this could lead to people passing on infections more easily — and indeed Omicron is believed to be more contagious than previous strains.

However, the virus was also found to grow 10 times slower in the lungs themselves, which authors of the study said could indicate it causes less severe disease.

Michael Chan Chi-wai, who led the study, noted that an individual’s immune response is also a major factor in the severity of disease, and in particular whether it is overstimulated, causing a “cytokine storm” — an excessive and damaging immune response, according to UK Guardian newspaper report about the research.

“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,” Chan Chi-wai said. “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.”

Data from the study, which has not yet been peer-reviewed, was published on the university website.

The Delta variant of COVID-19 triggered waves of infections around the world as it spread earlier this year.

Jeremy Kamil, an associate professor of microbiology and immunology at Louisiana State University Health Shreveport, explained to the Guardian that the findings indicate a possible advantage that Omicron has in spreading.

“It’s very likely spreading well even between vaccinated people, especially those who haven’t recently gotten a booster shot,” he said.

Following the detection of Omicron in South Africa just over a month ago, the global community has rushed to understand what danger the highly infectious mutation may present.

Many countries have imposed stiff measures, including Israel, which slammed shut its borders to foreign nationals and has built up a list of “red” countries that Israeli citizens are banned from visiting due to high infection rates.

On Wednesday the Health Ministry added seven countries to the no-fly list, including France, Spain and the United Arab Emirates.

Ireland, Norway, Finland and Sweden were the other four countries added to the list of countries to which Israelis will be barred from flying starting Sunday evening, as the government seeks to clamp down on the Omicron variant.

The list of red countries already includes the UK, Denmark and most of Africa.

The cabinet will convene on Thursday to ratify the Health Ministry’s decision.

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