Business

Scientists question origin of Omicron as variation spreads

Reports of a heavily mutated coronavirus variant first surfaced in late November after a jumbled batch of genomes was uploaded to a global database.

Omicron, as it is known, is traced back to a series of different cases: a university student in the South African capital of Pretoria, a diplomatic mission in Botswana and a South African tourist in a quarantined hotel Hong Kong.

As health officials worldwide try to stem the rapid spread of the variant, which has been detected in more than 50 countries on six continents, scientists continue to answer questions about its origins. its.

According to David Stuart, professor of structural biology at the University of Oxford, the mystery stems from the question of how “a bunch of mutations” came to be “under the radar”.

The genetic characteristics of Omicron are more similar to last year’s circulating viruses than to recent strains, such as Beta and Delta. Sarah Otto, professor of evolutionary biology at the University of British Columbia, said: “It appears to have been in hiding for a year.

Attempts to explain where and how Omicron quietly developed have given rise to competing theories.

The most common view among virologists is that it takes months to mutate in an immunosuppressed person with a chronic infection. Other ideas include accelerated evolution using anti-Covid drugs and crossbreeding into an animal that later jumped back into a human.

Diagram showing how to track the spread of viruses using their mutations

Given that South Africa was already facing its first wave of Omicron infections, it is most likely that this variant originated somewhere in the Middle East, according to Richard Lessells, an infectious disease physician at the University of KwaZulu-Natal in Durban. area.

A research team in South Africa, including Lessells, discovered an untreated HIV patient late last year who had been infected with Covid-19 for more than six months and gave rise to a chain of mutations affecting the mutant protein, part of the virus. most adaptations of Omicron are located. A UK study observed a similar process in a Covid patient with blood cancer.

The immune response of an untreated HIV patient would be “too weak to clear the virus but strong enough to drive evolution,” explains Lessells. He said the process would allow the coronavirus to mutate without being “caught” because many of these patients were asymptomatic and therefore were not tested.

“This evolutionary path may be rare, but it’s a good reason for the emergence of Omicrons,” said Lessells.

Image showing the main mutations forming the Omicron . variant

More than half of the 37.7 million people living with HIV in the world are in eastern and southern Africa. In South Africa alone, about 1.9 million people with HIV are undetected, untreated or poorly controlled, according to UNAIDs, the United Nations program on HIV/AIDS.

Jonathan Li, director of the Harvard/Brigham virology specialty lab in Boston, said it was “surprising” that two variants of interest – Beta and Omicron – had emerged in southern Africa, an area there are “large numbers of individuals immunosuppressed due to HIV Infection”.

“The collision of high case numbers, low vaccine availability and decades of the HIV crisis means that the chances of immunocompromised people carrying Covid for some time are very high,” said Otto. ,” said Otto. “It’s important to realize that many of these health crises are not independent of each other.”

Another theory about how Omicrons emerged in southern Africa has been advanced by William Haseltine, a virologist, who speculated that the mutations could be caused by Merck’s Covid-19 Antiviral Tablets. He noted that South Africa is one of the selected locations for the clinical trial of the drug molnupiravir, which will begin in October 2020.

The drug disrupts the virus’s ability to replicate by causing an explosion of errors that prevent it from spreading once the mutation reaches a certain level.

UK and EU regulators have authorized the emergency use of molnupiravir but some scientists, including Haseltine, have warned that its mutagenic properties are, in some cases certain combinations, can produce more dangerous variations. These concerns were also raised by outside experts at a meeting of the US Food and Drug Administration last week.

“It’s a very heavily mutated virus and that’s the kind of pattern you see with molnupiravir,” Haseltine told the Financial Times. “And the timing is right. I’m not saying it happened, but it could have happened. “

Merck told the FT that Haseltine’s “baseless allegations have no scientific basis or merit”.

A Merck spokesperson said: “There is no evidence to indicate that any antiviral agent has contributed to the emergence of circulating variants.

As more and more genomes are sequenced worldwide, researchers are beginning to piece together the origins of Omicrons. Each genome from regions with limited genomic surveillance, says Lessells, helps to understand the “missing branches” of the Omicron phylogenetic tree. More than 1,300 Omicron sequences have been uploaded to Gisaid, a global gene repository, since November 22.

According to Stuart Ray, a professor of medicine at Johns Hopkins University, recent sequencing has shown the idea that Omicrons have been spreading undetected for some time in an area not sampled by the kit test. genes are “increasingly unbelievable”.

“As we got more sequence data, it became clear that the genomes were tightly clustered,” explains Ray. “There would be more diversity if it went undetected.”

The theory that mutations arise in animals before being passed on to humans “isn’t completely unrealistic, but there’s little reason to believe it happened,” Ray added. “When you look at the movement of human viruses in animals, they accumulate mutations that are consistent with that host, not humans.”

Back in South Africa, medics and scientists stress that, no matter how Omicron emerges, the wealthier Western nations should learn the lessons of its evolution.

Professor Ian Sanne, director of the HIV research unit at the University of the Witwatersrand, said: “We’ll never find any patients. “But we must prevent history from repeating itself.”

“For the pandemic to end, we have to. . . address all regions of the world at once. I worry that Africa may be the last place to have an Omicron-specific vaccine, if it is needed. “

Additional reporting by Joseph Cotterill in Johannesburg.

Source link

news7h

News7h: Update the world's latest breaking news online of the day, breaking news, politics, society today, international mainstream news .Updated news 24/7: Entertainment, Sports...at the World everyday world. Hot news, images, video clips that are updated quickly and reliably

Related Articles

Back to top button