Is Delta the last super version of Covid? | Corona Virus

[ad_1]

Each week, a group of epidemiologists across the northeastern United States join a Zoom call that is entirely devoted to discussing the latest hints of new Covid-19 variants being reported around the world.

“It’s like a weather report,” says William Hanage, an epidemiologist at Harvard T.H. Chan School of Public Health. “It was like, ‘We have a little gamma in there, we have an alpha coming in here. “But now it’s just a delta.”

Since it was first detected in India in December 2020, the delta variant of Sars-CoV-2 has become so ubiquitous that it would be easy to assume that the virus’s rapid development has been replaced by a state of remission. According to the World Health Organization, 99.5% of all Covid-19 genetic sequences reported to public databases are now delta.

While new strains continued to emerge, such as the recent AY. 4.2 or the UK’s Delta Plus variant, which scientists estimate is 10-15% more transmissible, although there are no exact data for this yet, it’s almost identical to the Delta variant, apart from the single small mutation here and there . Hanage used to refer to them as the descendants of Delta.

“There were quite a few Delta Pluses,” he says. “I did a radio interview recently where I said that Delta Plus is an icon for anyone who gets their knickers right now. It’s not tremendously more portable.”

But the reason Hanage and his colleagues still check databases like Pangolin and Nextstrain every week, and the purpose of regular Zoom calls, is to try to predict what might happen next. Is it really the ultimate Covid-19 delta game or is there something ominous looming in the future? It’s a question that no one is quite sure of the answer to.

Inevitably there will be another important variable in the next couple of years – and delta may be overtaken by Professor Ravi Gupta, University of Cambridge

One possibility is that after the initial dramatic jumps in its genetic sequence, which led to first alpha, then delta, SARS-CoV-2 will now mutate slowly and steadily, eventually overtaking current vaccines, but only over the course of the cycle. for many years. While scientists try hard to point out that their predictions are mostly informed speculation, some see this as the most likely outcome.

“I expect that the type of evolution that we’ll see is what we call antigenic drift, where the virus gradually evolves to escape the immune system,” says François Balloux, director of the UCL Genetics Institute. “For influenza and other coronaviruses that we know well, the virus takes about 10 years to accumulate enough changes for antibodies in the blood to not recognize it.”

High levels of the virus increase the chance of dangerous variants developing. “If you look at the variables that we have, they all appeared in countries with very high, uncontrolled transmission,” says William Hanage of Harvard University. Photography: Dominic Lipinski/PA

But the alternative is the sudden emergence of an entirely new strain, with game-changing transmissibility, virulence, or immune evasive properties. Ravi Gupta, professor of clinical microbiology at the University of Cambridge, refers to these strains as “super variants” and says he is 80% sure another strain will emerge. The question is when.

“We have a delta pandemic right now,” Gupta says. “The new Delta Plus variant is relatively weak compared to the kind of things I’m talking about. It has two Delta breed booms, I don’t think it’s worrisome and hasn’t taken off very much in other countries. But there’s bound to be another important variant in the next couple of years that will compete with Delta and may outperform on delta”.

There are a number of ways this can arise.

Will we see a super alternative?

During the latter half of 2020, epidemiologists began noticing signs of a worrying phenomenon known as viral recombination, in which different copies of the SARS-CoV-2 virus exchanged mutations and combined to form an entirely new strain.

Fortunately, Gupta says that recombination doesn’t seem quite as common, but it remains a possible source of a new supernatural variant, particularly in parts of the world where large proportions of the population remain vulnerable and viral strains can spread freely. “Now that Delta is largely the main virus, this is becoming less and less likely,” he says. “But there are huge swaths of the planet that we haven’t sampled and we don’t know what’s going on. So it’s a real possibility.”

More complex mutations could develop in the future, which may be more problematic Professor Gideon Schreiber, Weizmann Institute of Science

The second is a series of major mutations, which either lead to a greatly improved version of delta or something completely different. He believes there is still plenty of room for that to happen. “While the latter variants are delta versions, the virus has enormous potential for future evolution,” says Gideon Schreiber, professor of biomolecular sciences at the Weizmann Institute of Science in Israel. “More complex mutations can evolve, with simultaneous mutations occurring in more than one locus, which may be more problematic.”

In recent weeks, there have been concerns that the use of new antiviral birth control pills, in particular Merck’s molnoperavir, could contribute to this by actively promoting Sars-CoV-2 to develop. Molnupiravir works by interfering with the virus’s ability to reproduce, contaminating its genome with mutations so that it can no longer reproduce. Some virologists have argued that if any of these viral mutations survive and spread to others, it could theoretically give rise to new variants. Others acknowledge that while this is worth watching, it is not a matter of concern to deprive critically ill patients of a potentially life-saving drug.

Gupta says the biggest problem, which is likely to lead to a supernatural variant, is the persistently high infection rate in countries such as the UK, due to delta’s ability to transmit between vaccinated individuals. “The higher the number of infections per day, the higher the chance that someone there, patient X, has the infection and the T cells are not strong enough to clear the infection because they are immunosuppressive,” he says. . “So they end up being infected over several days; they have some antibodies around because they have a partial response to the vaccine and the virus learns to evade it and then that spreads.”

Earlier this year, Gupta published a research paper that showed this process could occur in critically ill patients who were given convalescent plasma loaded with virus-killing antibodies. Since their immune system still couldn’t get rid of the virus, it learned to mutate around those antibodies. It has been speculated that the widespread use of convalescent plasma early in the epidemic was responsible for driving the emergence of variants.

“We don’t know for sure, but a lot of plasma was used and it was probably one of the variants driving it,” he says. “It has been used very widely in Brazil, India, the United Kingdom and the United States, all of whom have developed their own sets of variants.”

Vaccine arms race

Epidemiologists are now trying to model what the new super variable might look like. So far, major shifts in the virus have helped increase its transmissibility. Hanage explains that one of the reasons the delta variant has such an effect is that it grows so rapidly inside human cells, before the immune system is even going to work. As a result, delta infected people carry nearly 1,200 times more viral particles in their nose than the original SARS-CoV-2 strain and develop symptoms two to three days earlier.

This is the result of natural selection. Different versions of the virus are being created all the time, but the ones that survive and become more prevalent are the ones that are best able to infect new people. However, in countries like the UK, where the proportion of the unvaccinated population is declining, this could start to change. Strains that can evade the antibodies are more likely to become more dominant, making the next super variant much more likely to be able to evade at least some parts of the immune response.

Concerns have been raised that because of the way Merck’s antiviral drug Molnupiravir works, new mutations will be generated. However, most scientists do not expect these substances to be harmful. Photo: Merck & Co./Reuters

“The strains of the virus that end up surviving and becoming dominant vary, depending on what stage of the pandemic you’re in,” Hanage says. “So far, it has been critical for the virus to be effectively transmitted to the remaining group of unprotected people. But that is now expected to change.”

While this may sound a little intimidating, it’s not all bad news. Because Covid-19 vaccines are designed with viral evolution in mind, epidemiologists do not anticipate any new super-variable that would render them completely useless, and therefore unlikely to lead to severe outbreaks, such as those that have occurred in the past two years.

In addition, a second generation of Covid-19 vaccines has been developed. Vaccine developer Novavax hopes to gain regulatory approval for its vaccines in the next two months, while several more vaccines are expected to be on the market between now and 2023. These platforms are taking their own steps to combat potential future variants.

You want to limit the number of chances the virus gets to roll the dice William Hanage, epidemiologist

According to Karen Goss, executive vice president and head of research and development at US pharmaceutical company Gritstone, which has a second-generation Covid-19 vaccine in phase I clinical trials, the companies are sequencing all existing strains of Sars-CoV-2 and aiming to generate Neutralizing antibody responses against regions of the virus are conserved among all those strains.

But epidemiologists also believe that relying on vaccines alone is not enough. Gupta says that even as we try to find a way to live with Covid-19 in the UK, there should still be some restrictions in place to limit the spread of the virus and reduce the number of chances it gets to mutate.

“The case numbers are very high right now, and it’s much better to prevent new infections,” Gupta says. In other words, we should not walk around crowded places, in buildings without masks, although it is difficult to do so. If you look at the variants we have, they all appeared in countries with very high, uncontrolled transmission – India, UK, Brazil. There is a reason we haven’t heard of the Singaporean or South Korean alternative.”

It’s a philosophy that many of his colleagues agree with. “You want to limit the number of chances the virus gets to roll the dice,” Hanage says. “With natural selection, you’re basically talking about the most creative force that we know when it comes to solving problems. It’s amazing. That’s why you’d never bet on it. We expect the virus to continue to evolve.”

[ad_2]