The Omicron variant causes milder disease than previous versions of the coronaviruses, according to a series of new studies on lab animals and human tissues.
In studies on mice and hamsters, Omicron produced less damaging infections that were limited to the upper airway. The variant did less harm to the lungs than previous versions.
The idea of a disease that affects the upper respiratory system is emerging, according to a Berlin Institute of Health Computational Biologist.
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.
The behavior of the virus can't be predicted from just the genes.
Over the past month, more than a dozen research groups, including Dr. Gupta, 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.
The majority of Omicron infections were in young people, who are less likely to get seriously ill with all versions of the virus. Many of the early cases were happening in people with immunity from previous infections. It was not clear if Omicron would prove less severe in an unvaccinated older person.
Experiments on animals can help clear up the ambiguities. More than half a dozen experiments made public in recent days all pointed to the same conclusion: Omicron is milder than Delta and other earlier versions of the virus.
A group of Japanese and American scientists released a report on hamsters and mice that had been exposed to Omicron. The study found that people who were exposed to Omicron had less lung damage, lost less weight and were less likely to die.
The results of Syrian hamsters, a species known to get severely ill with all previous versions of the virus, were particularly struck by the scientists.
The study found that every other variant of the hamsters has robustly infectious them.
The same conclusion has been reached in several other studies on mice and hamsters. These studies have been posted online but have not yet been published.
A researcher at the University of Cambridge. He said that you can't predict the behavior of virus from just the genes.
Omicron may be milder because of its structure. The hamsters had the same level of Omicron in their noses as animals with an earlier form of the coronaviruses. The Omicron levels in the lungs were not as high as other versions.
Researchers at the University of Hong Kong studied bits of tissue taken from human airways during surgery. The researchers found that Omicron grew more slowly than Delta.
The bronchi are tubes in the upper chest that carry air from the windpipe to the lungs. Omicron grew faster than Delta or the original coronaviruses inside of the bronchial cells in the first two days after an infection.
These findings will have to be followed up with more studies, such as monkeys or people with Omicron. If the results hold up, they could explain why people with Omicron are less likely to be hospitalized than those with Delta.
The nose and mouth are where coronaviruses start. Mild infections don't get much further than that. The coronaviruses can cause serious damage when they reach the lungs.
Immune cells in the lungs can overreact and kill off other cells. They can cause inflammation that can damage the lung. The viruses can escape from the damaged lungs into the bloodstream and cause a lot of problems.
Dr. Gupta thinks that the new data gives a reason why Omicron doesn't fare well in the lungs.
TMPRSS2 is on the surface of many cells in the lung, which can help pass viruses onto the cell. Dr. Gupta and his team found that thisProtein doesn't grab on to Omicron very well. Omicron does a worse job of infecting cells than Delta does. A team at the University of Glasgow came to the same conclusion.
coronaviruses can slip into cells that don't make TMPRSS2. The evidence that Omicron is found more often in the lungs is due to the fact that cells in the airway don't carry the proteins.
Dr. Gupta speculated that Omicron evolved into an upper-airway specialist. If that is true, the virus might have a better chance of being expelled in tiny drops into the surrounding air.
He said that it was all about what happened in the upper airway. The severe disease stuff happens down below in the lungs. The virus has evolved in this way.
The studies help explain why Omicron causes milder disease, but they don't know why the variant is so good at spreading. The United States had more than 580,000 cases on Thursday, the majority of which are thought to be Omicron.
Sara Cherry, a virologist at the Perelman School of Medicine at the University of Pennsylvania, said that these studies address the question of what may happen in the lungs but don't really address the question of transmissibility.
The hypothesis that TMPRSS2 is the key to understanding Omicron was endorsed by Dr. Diamond, but he wanted to wait for more studies to be carried out. He said that it was still premature to talk about this.
Scientists know that part of Omicron's contagiousness comes from its ability to evade the immune system, allowing it to get into the cells of people who have been vaccined. They suspect that Omicron has other advantages.
Researchers reported last week that the variant carries a variation that may weaken our innate immunity, a molecule alarm that is activated quickly in the nose. It will take more experiments to see if this is one of Omicron's secrets to success.
It could be as simple as the person has a lot more virus in their saliva and nose. It could be more stable in the air or better at spreading infections. She said it was an important question.
