The first indication of why the Omicron variant causes milder disease than previous versions is provided by a series of new studies on lab animals and human tissues. In studies on mice and hamsters, Omicron produced less damaging infections, often limited to the upper airway: the nose, throat and windpipe. The variant did less harm to the lungs than previous versions. "It's fair to say that the idea of a disease that manifest itself primarily in the upper respiratory system is emerging," said Eils, who has studied how coronaviruses affect the airway. The first report on the Omicron variant came out of South Africa in November, and scientists were only able to guess at how it might behave differently from earlier forms of the virus. They knew that it had a lot of genetic variations.
Some of the genes that were shown to enable coronaviruses to grab onto cells were found in these. The early line of defense against infections was allowed to be evaded by others. How the new variant would behave inside the body was a mystery. "You can't predict the behavior of the virus from just the genes," said Gupta. Over the past month, more than a dozen research groups, including Dr. Gupta's, have been observing the new pathogen in the lab, infecting cells in petri dishes with Omicron and spraying the virus into the noses of animals. Even people who had recovered from infections were infecting others with Omicron as they worked. hospitalizations increased only modestly as cases skyrocketed. Omicron was less likely to cause illness in people who had been vaccineed, according to early studies. There were a lot of things that came with the findings.
