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How the Covid pandemic ended: What comes after Omicron?

As a weary world faces its third year of coronavirus, as its spread is sped up by the most contagious variant to date, many scientists are optimistic that the pandemic is on health. global will decrease by 2022.

Although Coronavirus variant Omicron threatens a crisis within the next few months, the most likely scenarios show a much improved outlook thereafter due to increasing immunity in the global population, through vaccination and natural infection. However, there is the potential to make the consequences of the virus less severe.

“The increase in Omicron cases in Europe and North America is extremely rapid, and we could see an equally rapid rate of decline over the next month or two, although it could take four to five years. It took six months for this variant to be reverberated around the world,” said Sir Jeremy Farrar, director of the Wellcome health organization.

After the Omicron wave passes, “immunity is built up that has the potential to give us a period of calm, but there are a number of ways this can happen,” he said.

An encouraging sign came on Thursday as South Africa, where Omicron was first recorded in November, lifted restrictions on the movement of people as cases increased. “All indicators suggest that the country may have passed the peak of the fourth wave,” a cabinet statement said.

Tim Colbourn, a professor of epidemiology at University College London, said it was “completely reasonable to think that the burden of Covid could be reduced by 95% by 2022, so that it is no longer a leading health problem. That would be a reasonable goal to end the pandemic.”

Some experts see Omicrons as indicative of the future evolution of the Sars-Cov-2 virus, as natural selection favors mutations that transmit as quickly and efficiently as possible between individuals. who already have some measure of immune protection.

Lab tests show that mutations in Omicron have made it more infectious than earlier variants in the upper respiratory tract and nose – prone to rapid transmission – but conversely less likely to penetrate deeply into the lungs, where it tends to do the most damage.

These conclusions are supported by epidemiological evidence that reduce the risk of serious illness half or more with Omicron.

Omicron’s high transmissibility means 3 billion infections globally within the next two months, as much as in the first two years of the pandemic, according to a model by the Institute for Health Metrics and Evaluation in New York. University of Washington.

“But this massive increase in infections and cases will translate into fewer hospitalizations than the Delta wave or peak last winter in the acute phase,” said Chris Murray, director of the institute. global level”.

The evidence to date suggests that Omicron will replace Delta as the variant circulating in most of the world, just as Delta has wiped out earlier strains. “I’m very reassured by that prospect,” Farrar said.

“I would be more concerned if you had different variants circulating at the same time, as that would mean they were exploiting different ecological niches and we would end up with a potentially dangerous dynamic. of many interacting strains.”

People line up for antigen testing in Portugal

People line up to take a Covid test in Portugal © Horacio Villalobos / Corbis / Getty Images

Even if Omicron does indeed become the dominant strain, another variant of the virus is certain.

While individual changes to the genetic code are random events in a virus’s replication – and no one can predict it. variety of mutations specific to Omicrons – environmental pressures that allow certain organisms to grow predictably.

A world where most people were exposed to Sars-Cov-2 would favor variants that transmit quickly and easily while avoiding the attention of the human immune system. Mutations that make the virus more lethal are unlikely to make it stronger and can even be a defect if they interfere with efficient transmission.

“Although you can imagine a deadly new variant emerging that is more contagious, it is also more harmful. . . I don’t know how viable this virus is,” said Jennifer Rohn, a cell biologist and UCL University professor. “Sars-Cov-2 relies on infecting cells and it may have been close to reaching the limit of its repertoire.”

Whether new pathogens tend to become milder over time as they form in human populations is a matter of debate among scientists. But Paul Hunter, a professor of medicine at the University of East Anglia, believes that’s true for the coronavirus.

Four human coronaviruses, which have long circulated worldwide causing mild to moderate cold-like symptoms, may have caused serious epidemics when they first transferred from animals to humans.

In particular, the most recent occurrence, OC43, crossed with cattle around 1889 and caused the pandemic then known as “Russian Flu”Hunter believes that causes milder episodes of the Covid-like illness over four or five years – although not everyone is convinced by the evidence.

“Sars-Cov-2 will continue to produce new variants forever, but our cellular immunity will strengthen our defenses against serious illness every time we become infected,” he said. . “Finally, we won’t have to worry about that anymore.”

That reassuring scenario might apply if Sars-Cov-2 develops in a fundamentally linear fashion. There is, however, a small risk that an evolutionary leap suddenly jumps to “something out of the field that doesn’t come from the existing lineages,” points out Farrar.

One possibility is that Sars-Cov-2 evolved in animal populations and then reverted back to humans. Flu pandemics usually begin with an influenza virus that jumps from birds or pigs.

Or Sars-Cov-2 could swap genes with another virus through “gene recombination”. For example, if someone were infected concurrently with Sars-Cov-2 and the related Mers coronavirus, which is not easily human-to-human but kills about 40% of those infected, one could imagine a hybrid nightmare arose. combination of transmissibility and lethality.

While such an evolutionary leap is not impossible, most experts consider it extremely unlikely. “I’m much more scared of another pandemic caused by a new virus that we don’t know yet than some variant of Sars-Cov-2,” Colbourn said.

https://www.ft.com/content/b3aa95ed-18b3-406a-b611-9845dd07bbbc How the Covid pandemic ended: What comes after Omicron?

Huynh Nguyen

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