What we know about the Omicron variant that sparked global concern

With cases of the omicron coronavirus variant discovered worldwide, researchers are racing to understand the effects of genetic mutations, which far exceed the number for any previous variant.

The 50 mutations include more than 30 mutations on the skeletal protein, the exposed part of the virus that binds to human cells. Scientists fear that these changes make it more transmissible than the dominant delta variant and more likely to evade the immune protection offered by vaccines or previous infections.

How upset are we with Omicron?

The world’s virology labs have only had a few days to investigate Omicron since scientists in South Africa and Botswana alerted the world about its presence on November 23. It’s unlikely that definitive evidence about her behavior will emerge for another week or so, although we can expect to hear some tentative results.

The concerns are mainly fueled by Omicron’s unusual genetic profile. Jeffrey Barrett, director of the Covid-19 Genome Initiative at the Wellcome Sanger Institute, described it as an “unprecedented sample” of mutations from four previously worrisome variants: Alpha, Beta, Gamma and Delta, along with other changes never seen before. . The significance is not yet known.

Fifteen of the mutations are in the receptor-binding domain that acts like a “grappling hook” for the virus to enter human cells, said Jacob Glanville, a computational immunologist and founder of Centivax, a US therapeutic company.

Diagram showing the main mutations that make up the Omicron variant

These mutations are expected to help the virus bypass the body’s immune system, which was trained by infection or previous vaccination to fight the original strain first discovered in Wuhan.

Many of the Omicron mutations came “out of the blue” and had not been observed before in other strains, said Solomir Kubik, a genome research expert at Geneva-based biotech company Sophia Genetics.

Therefore, scientists “have very little insight into what these new mutations do to how the virus works,” he explained, adding that once it starts spreading widely, its “true fitness” will become apparent.

Some mutations indicate increased transmissibility, while changes in the genetic code make it difficult for the immune system, trained by existing vaccines or previous infection with another variant, to handle a new strain. But it will take several weeks before researchers can determine the interactions between them and their cumulative effect.

How fast does an omicron spread?

Although Omicron was first discovered in samples from southern Africa, no one knows for sure where it originated and how many changes accumulated. The preferred theory is that the variant evolved in one individual whose immune system was compromised by medical treatment or disease – “an evolutionary gym,” said Sharon Peacock, professor of public health and microbiology at the University of Cambridge.

Omicron spreads rapidly in South Africa, particularly in Gauteng County, which includes the cities of Johannesburg and Pretoria. Testing there has shown that it is responsible for more than 90 percent of all infections. The seven-day average daily cases in South Africa rose fourfold to 2,756 in the week ending November 30.

The chart shows that the Omicron variant is driving a new wave of infections in South Africa

waste water analysis In Pretoria, to track the impact of SARS-Cov-2 – an indicator of the scale of the outbreak – until the week ending November 19, it indicates that infections rose near levels last seen in the run-up to the peak of the delta wave in July.

Outside of Africa, cases of the Omicron variant have been reported in more than 20 countries in North and South America, Europe and Asia – although there are so far a few rather ubiquitous rather than large-scale community transmission reported in South Africa.

Although the speed with which cases are increasing in South Africa suggests that Omicron may be more contagious than Delta, epidemiologists say it may not be transmissible in other parts of the world where populations are older and more vaccinated.

Is there any evidence that Omicron produces less severe disease than previous variants?

Even if Omicron has been shown to be the most infectious Sars-Cov-2 species to date, there is no clear evidence yet from South Africa or elsewhere about whether it will cause worse symptoms. “It could go either way,” said Centivax’s Glanville. “Mutations can make it worse or mutations can make it milder.”

Several doctors in South Africa note that people with Omicron have milder symptoms than those in Delta patients. Many symptoms. Others suffer from coughing, fatigue, body aches and headaches.

No deaths have yet been attributed to the new variant, although it mostly affected young adults less susceptible to severe symptoms, whatever variant was responsible.

“I think it will be a mild illness, we hope,” said Angelique Coetzee, president of the South African Medical Association. “We are confident we can handle it.”

Michael Mina, an epidemiologist at Harvard Medical School, noted that the number of cases reported in Pretoria was relatively small compared to the high viral load detected in wastewater.

While this may mean that most infections were too mild to go undetected, it is likely that wastewater will be a leading indicator and that case numbers will catch up. “There is not much in this virus [genetic] The sequence suggests that it should be very mild,” he said.

Even if Omicron caused milder symptoms on average, the total number of hospitalizations and deaths would be greater if it was more contagious and better at escaping human immune protection.

How effective are Covid vaccines against Omicron?

Vaccine manufacturers and academics are working around the clock to assess the effectiveness of strikes developed to combat the original Wuhan virus against the Omicron variant.

The major players have offered different opinions so far, while emphasizing that it is too early to present hard facts. Stéphane Bancel, CEO of Moderna, said current vaccines are likely to be much less effective against Omicron, while Ugur Sahin, his BioNTech counterpart, said that “fully vaccinated individuals will still have a high level of protection against severe diseases that induced by Omicron”.

The graph shows that Omicron appears to outperform the other variants much faster than the previous worrisome variants

Most experts expect early laboratory studies to show a marked decrease in antibody protection, but vaccination-induced cellular immunity, which is difficult to assess, may hold up better.

Francois Ballou, director of the UCL Genetic Institute in London, said the new alternative was “unlikely to completely escape the immunization provided by vaccination and previous infection”. “With high vaccination rates and promising drugs on the horizon, possible [Omicron] The wave should be much less painful for the weather than alpha and delta waves.”

Epidemiology in South Africa will provide another source of evidence about vaccine efficacy by measuring rates of infection and serious disease caused by Omicron in people who have received vaccines.

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