May 22, 2022

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Omicron, where does the alternative come from? The three hypotheses of scientists about the origin – Corriere.it

from Christina Maroney

Mutations may accumulate in an immunosuppressed patient, in a population with poor viral surveillance or in an animal reservoir (possibly mice) giving rise to ‘reverse zoonoses’

Since South African scientists announced that they have identified a new and worrisome species, which has been baptized Omicron DWorld Health OrganizationThe world is eagerly waiting to know How dangerous is this new strain really , What is its impact on the epidemic and vaccines. But there is another question that scientists around the world are asking: Where does Omicron come from? Currently, scientists are formulating hypotheses and it is not taken for granted that one day we can really shed light on the origin of a variant with such strange properties.

Evolution under the radar

It seems quite clear that Omicron did not evolve from one of the earlier variants of anxiety such as alpha NS delta. In fact, Omicron looks very different from the millions of Sars-CoV-2 genomes that have been shared over the course of months. Based on the genetic profile, Emma Hodcroft, a virologist at the University of Bern, speculates that Omicron may go back to the middle of 2020, she wrote. Science. Looks like Omicron does Developed in parallel with other variables, hidden. The virologist comments: “It is difficult to find a first-degree relative, who may have quickly diverged from other strains.”

The three hypotheses

But where did Omicron’s ancestors hide for more than a year? There are three possible explanations according to scientists.
1- The virus may have spread in one Population with poor viral surveillance and no sequence
2- It could be a virus I am from an immunocompromised patientunable to eradicate covid
3- The virus may have occurred andRequired in non-human species And only recently has it been possible to make the species jump to humans (reverse zoonosis)

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Reverse zoonosis hypothesis

Some scientists think the virus may be hiding rodents Or in other animals and not in humans, and therefore underwent many of them evolutionary pressures This leads to the emergence of new mutations before returning to humans. Christian Andersen, an immunologist at the Scripps Research Institute, is among those who have put forward the hypothesis that Omicron may have originated from Reverse zoonosis (A zoonotic event occurs when an animal pathogen begins to spread to humans and a reversible zoonotic event occurs when that virus returns to an animal species.) “I know most scientists think -,” said Andersen. STATThe variants come from immunosuppressed individuals, which is reasonable. But to be honest, I think infection with a new zoonotic virus is likely to take into account that many of the mutations are somewhat unusual and that the strain appears to have undergone early separation from other variants of the coronavirus. This possibility cannot be ignored.

Adaptation to rodents

According to investigations Robert Garry, Professor of Microbiology and Immunology at Tulane Medical College, Omicron Seven mutations that would allow the variant to infect rodents such as mice, rats and similar species. Other variants like Alfa for example only carry some of these mutations. In addition to “rodent adaptation” genetic mutations, Omicron brings about a number of changes not seen in any other version of Sars-CoV-2, and many scientists view this as a possibility Evidence that the variant appeared in a host animal.

white-tailed deer case

“It is interesting to see how incredibly different the Omicron is from the other variants,” comments Science evolutionary biologist Mike Woruby from the University of Arizona in Tucson, noting that 80% of white-tailed deer Tournaments held in Iowa between late November 2020 and early January 2021 were carriers of Sars-CoV-2. There may be – some scientists speculate – other animal species, besides white-tailed deer, that are also chronically infected and this may lead to selective pressure over time. One studio A post online a month ago indicates that white-tailed deer What is known as a reservoir for Sars-CoV-2 could become: Animals can carry the virus indefinitely and periodically spread it to humans. “If this were the case, it would kill any hope of eradication or eradication of the virus in the United States and thus from the world” – says veterinary virologist Suresh Kochipudi from Pennsylvania, who co-administered the study. “It is too early to dismiss any theory of the origin of the Omicron,” he says. Ares Katzorkis, an evolutionary biologist from the University of Oxford who is skeptical of the animal scenario given the large number of human infections. “I would start to worry about the animal reservoirs if we could kill the virus and then we could find somewhere to hide among the animals.”

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Omicron hunting in animals

Scientists are already examining different types of animals to see if they can be infected with Sars-CoV-2 and looking for traces of omicron. To understand whether Omicron could indeed be the result of a reversible zoonotic disease Michael Worby He suggests experimenting with selected species of wild animals to see if they can become infected, and once infected, if similar viral development patterns to those observed in Omicron occur. One distinguishing feature of Sars-CoV2, as virologists describe it, is that it is a dysfunctional virus capable of infecting a number of species, including Pet dogs and cats, mink, white-tailed deer Given the ease with which the virus appears to be transmitted from one species to another, it is possible that the list of animals capable of hosting the coronavirus could grow.

Weak viral surveillance hypothesis

Some other scholars like Christian Drosten, a virologist at the Charité University Hospital in Berlin, supports the theory that Omicron has been spreading “while you sleep” for some time. “I suppose this new strain did not develop in South Africa, where a lot of the sequences are taking place, but elsewhere in South Africa during the winter spell.” Andrew Rambaut, evolutionary biologist
On the other hand, the University of Edinburgh believes it is unlikely that the virus will remain hidden among a group of people for long: “I’m not sure there is a place in the world that is isolated enough to allow this type of virus to be transmitted for long before it appears in other areas.”

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Chronic infection hypothesis

Instead, Rambaut and several other scientists suggest that the virus likely evolved in Patient with chronic Covid-19 infection, perhaps a person whose immune response to another disease or drug has been compromised. When alpha was first discovered in late 2020, it appeared to have acquired several mutations at the same time, leading researchers to speculate that it was caused by a chronic infection. In South Africa, one case has been documented A woman infected with HIV The untreated case has remained positive for Sars-CoV-2 for more than six months. The virus accumulated a number of mutations observed in variants of concern. People who are already immunocompromised can act as a “reservoir” for variants, where they can harbor the virus for several weeks – enough time for it to mutate.

Dec 3, 2021 (change on Dec 3, 2021 | 13:38)