The three hypotheses of scientists about the origin of the omicron variant: the theory of reverse zoonoses

Since South African scientists announced that they had identified a new disturbing variant, later called omicron by the World Health Organization, the world has

The three hypotheses of scientists about the origin of the omicron variant: the theory of reverse zoonoses

Since South African scientists announced that they had identified a new disturbing variant, later called omicron by the World Health Organization, the world has been anxiously waiting to know how dangerous is this new variant, what impact will have on the pandemic and in the vaccines. But there is another question that scientists from all over the world are made: where does omicon come from? For now, scholars are formulating hypotheses and is not assumed that one day really can write light on the origin of a variant with such strange characteristics.

It seems quite evident that omicron was not developed from one of the previous worrisome variants, such as Alpha or Delta. In fact, omicron is very different from the millions of SARS-COV-2 genomes that have been shared over the months. According to the genetic profile, Emma Hodcroft, Virologist at the University of Bern, speculates that omicron can be traced back in mid-2020, writes in Science.

It seems that omicron evolved in parallel with the other variants. "It's hard to find a close relative of his, probably he soon separated from the other strains," says virologist.

But, where have you been hiding the omicron predecessors for more than a year? There are three possible explanations according to scientists.

Some scientists think that the virus may have hidden in rodents or other animals instead of in humans and, therefore, to suffer several evolutionary pressures that gave rise to new mutations before returning to humans.

Kristian Andersen, immunologist from the Scripps Research Institute, is among those who have raised the hypothesis that omicron could have emerged from reverse zoonosis (a zoonotic event is when an animal pathogen begins to spread to humans and a reverse zoonosis is when This virus returns to an animal species).

"I know that most scientists think," Andersen said, "the variants come from immunosuppressed individuals, and this is plausible. But, to be honest, I think it is more likely a new zoonosis considering that many mutations are something. Unusual and that the strain seems to have suffered an early division of other variants of Coronavirus. This possibility should not be ruled out. "

According to Robert Garry's research, professor of microbiology and immunology at the Tulane Medicine School, ÓMicron has seven mutations that would allow the variant infects rodents as mice and rats and similar species.

Other variants such as alpha, for example, carry only some of these mutations.

In addition to the genetic mutations of 'adaptation of rodents', omicron produces a series of changes that are not seen in any other version of Sars-COV-2, and many scientists see this as a potential evidence that the variant emerged in an animal invited.

"It is interesting to observe how incredibly different is omicron from the other variants," says evolutionary biologist Mike Worobey of Arizona University in Tucson in Science, and points out that 80% of white-tailed deer sampled in Iowa between the end of November. 2020 and early January 2021 were carriers of SARS-COV-2.

There may be, some scientists speculate, other animal species, in addition to the white-tailed deer, also chronically infected and this could lead to a selective pressure over time.

A study published a month ago suggests that the white-tailed deer could become what is known as a reservoir of SARS-COV-2: animals can behave the virus indefinitely and transmit it periodically to human beings.

"If this is the case, it would destroy any hope of eliminating or eradicating the virus in the United States and, therefore, in the world," says Veterinary Virologist Suresh Kuchipudi by Penn State, who co-controlled the study.

"It is too early to rule out any theory about the omicron origin," says Aris Katzourakis, an evolutionary biologist at the University of Oxford, which is skeptical of the animal scenario given the high number of human infections.

"I would start worrying more about animal reservoirs if we could kill the virus and then I could find a place to hide in animals."

Scientists are already examining several animal species to see if they can become infected with SARS-COV-2 and look for omicron traces. To understand if omicron could really be the result of a reverse zoonosis, Michael Worobey suggests experimenting with selected species of wild animals to see if they can become infected and, once infected, if viral evolution patterns similar to those observed in omicron.

One of the distinctive characteristics of SARS-COV2 is that, as virologists describe it, it is a promiscuous virus capable of infecting several species, including domestic cats and dogs, visions and white-tailed deer. And given the ease with which the virus seems to move from one species to another, it is possible that the list of animals capable of harboring the Coronavirus may grow.

Other scientists, such as Christian Drosten, virologist at the University Hospital Charité in Berlin, support the theory that ÓMicron has been circulating "Sleeping" for a long time.

"I guess this new strain did not evolve in South Africa, where many sequences are taking place, but somewhere else in South Africa during the Winter Ola."

Andrew Rambaut, an evolutionary biologist at the University of Edinburgh, believes that it is unlikely that the virus has remained hidden in a group of people for so long: "I'm not sure that there really is a place in the world isolated enough to be for Allow this type of virus to spread, transmit for a long time before it arises in other areas. "

Instead, Rambaut and several other scientists suggest that the virus has been developed in a patient with chronic infection by Covid-19, probably someone whose immune response has been compromised by another disease or drug.

When Alpha was discovered for the first time at the end of 2020, it seemed to have acquired numerous mutations at the same time, which led researchers to speculate that it was the result of a chronic infection.

A case of a woman infected with HIV in South Africa has been documented. The virus has accumulated a series of mutations observed in the variants of interest.

The immunosuppressed people could act as a "reservoir" of variants, as they can house the virus for several weeks, enough time for mutar.

Date Of Update: 08 December 2021, 11:30

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