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Rapidly Spreading Yet Less Damaging

New animal studies provide additional evidence that the omicron variant of SARS-CoV-2 is less likely to damage the lungs compared with other variants, resulting in milder disease, The New York Times reported Friday. While early data indicated that omicron carried a large number of mutations that enhanced its infectivity, including in vaccinated or previously infected people, the virus also appeared to cause less severe disease.

By infecting mice and hamsters with different variants of the virus, groups of investigators in the US, Asia, and Europe have confirmed that omicron caused less lung damage and was less lethal, mostly infecting cells within the upper airway. Separate experiments also found that omicron grew faster in bronchial tissue and that it does a poorer job of binding to TMPRSS2, a protein expressed on the surface of many cells within the lungs but not in upper airways, versus other variants. This, the New York Times writes, suggests that omicron has evolved into "an upper-airway specialist, thriving in the throat and nose.

Despite the findings around why omicron is less dangerous than other SARS-CoV-2 variants, the reasons behind its high transmissibility remain unclear. It may be a result of its ability to evade antibodies or to weaken innate immunity, but additional research is needed.