The new year has seen a flurry of omicron cases, but will these be the last of the variants, or will an entirely new ‘disturbing variant’ appear in 2022?
Experts tell Live Science they wouldn’t be surprised if it’s a disturbing new Corona Virus Different crops this year – but it’s hard to predict how quickly this species will spread, and how far it will be avoided by humans immune system Or whether it will cause more serious illness than previous versions of virus.
The omicron variant gained an advantage over delta because it is highly transmissible and because it can evade the immune defenses of previously vaccinated and infected people. This allowed the variant to infect a part of the population that deltas could not easily infect, said Kartik Chandran, a virologist and professor of microbiology and immunology at Albert Einstein College of Medicine in New York City. Likewise, to compete with omicron, future variants of concern will need to make similar gains in both transmissibility and immune evasiveness.
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“There is no reason to believe that the virus has genetically run out of place,” he said. “I expect we’ll see more variants, and we’ll see similar types of wave-like behavior,” which means higher rates of infection after a new variant is introduced.
But while the next problem variant may easily spread and outpace the immune system, the course of its other traits, such as virulence — the severity of disease caused by the virus — remains unclear.
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Given the current rate of coronavirus infection worldwide, and the mutation rate of SARS-CoV-2, “new variants are expected,” Karen Mosman, professor of pathology and molecular medicine at McMaster University in Ontario, told Live Science. in a letter. But as we’ve learned over the past two years from pandemicNot every new variant will be competitive enough to take over, she said.
Future variables can gain a competitive advantage in several ways. In theory, Mossman said, one of these potential pathways could lead to a virus that transmits more omicron while causing less severe disease.
“Viruses need to circulate and spread to new hosts. The most successful viruses do this by spreading rapidly without causing symptoms,” Mossman said, because an infected host can move easily and pass the bug to additional hosts. “It is not beneficial for the virus to kill its host before it spreads.”
Omicron may be less likely to cause severe disease than previous variants, Live Science previously reported. This may be in part because it grows more easily in the upper airways and less well in the lungs – which may also help the variant spread more easily. In this case, it appears that the virus may have evolved to be less virulent as a result of its increased ability to jump between hosts.
Mossman noted that there is no guarantee that the next worrisome alternative will achieve the same trade-off. “A group of mutations that provide a selective advantage may also lead to more serious disease,” she said.
For example, mutations that give the virus the ability to reproduce incredibly quickly, or escape the clutches of Antibodies Which prevents them from entering cells, can increase the likelihood of the insect causing a severe infection. Delta showed such a combination of traits, in that it spreads more easily than all previous variants of the coronavirus while still doubling the risk of hospitalization for unvaccinated people, compared to Alpha, The New York Times reported. Immunity deficiency Virus And Ebola are examples of viral diseases that have not evolved to become less severe despite having been around for decades; smallpox It was another example, before it was eliminated.
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Chandran said the idea that the virus might become less virulent over time “certainly isn’t illogical as a hypothesis,” but agreed with Mosman that this outcome is uncertain. He noted that often, as viruses replicate and pick up mutations, individual mutations within their genomes interact with each other and can produce unexpected traits. This phenomenon, called epistasis, makes it very difficult to predict the development and behavior of future variables.
The Great Unknown
In general, there are physical and hereditary Chandran noted the limitations on how advanced SARS-CoV-2 can be. Some of these restrictions prevent the virus from becoming infinitely more contagious, which is why scientists expect that the transmissibility of the virus will eventually stabilize and stop increasing, I mentioned nature.
On a physical level, “viruses have to walk this fine line between stability and instability,” Chandran said, and this balance limits their transmissibility. A virus is a microscopic box full of genetic material, and that box must be strong enough to keep the genetic material safe in the body and in the outside world. But to infect cells, the box must be opened to get the virus’ genetic material out. Very stable, the virus cannot open and infect cells efficiently; It’s very unstable, Chandran said, and the virus won’t live long after it’s dribbled in someone’s sneeze.
And at the genetic level, the virus can only accumulate so many mutations before it starts to malfunction, he said.
For example, the virus needs its spiky protein to fit snugly over the receptors of human cells in order to provoke infection. Spike mutations can help the microbe to hide from antibodies to previous variants; The omicron carries about 30 spikes in its height, some of which help the variant evade the immune system. Chandran said there is likely to be a limit to the number of mutations a spike can take in before its ability to deliver to human cells begins to falter.
In this regard, it is possible that the virus still has room for genetic maneuver. Based on a recent study published on December 2 in the journal Science, SARS-CoV-2 likely tolerates a large number of escape mutations – those that help the insect evade antibodies – while retaining its ability to contact human cells. “The great structural flexibility we saw in the SARS-CoV-2 spike protein suggests that the omicron is not likely to be the end of this virus story,” said senior study author Dr. Jonathan Abraham, associate professor of microbiology at Harvard Medical School and pathologist. Infectious at Brigham and Women’s Hospital, He told the Harvard Gazette.
Other unknowns make it difficult to predict the future evolution of SARS-CoV-2. One big question, Chandran said, is where the next variant of the concern will come from, since it may not be descended from an omicron. Omicron originated from a different branch of the coronavirus family tree than delta, although delta was prevalent at the time; The following variant may have a similar origin story.
Meanwhile, coronavirus host animals are another alternative card.
SARS-CoV-2 can infect a variety of animals, including minks, ferrets, cats, white-tailed deer, and many primates. I mentioned nature. This raised concerns that the virus, as it spreads in animals, could pick up mutations that make the insect more contagious or lethal to humans, or undermine the effectiveness of our vaccines. For this scenario to unfold, the coronavirus would need to return to humans after infecting an animal, and in some cases, the virus may mutate so much that it cannot return to humans, Chandran noted. “The genetic pathway of the virus can be quite different in these other hosts,” he said.
However, cases of animal-to-human transmission were reported in mink farms early in the epidemic, and it is also possible that other species could transmit the virus to humans, Live Science previously reported. For this reason, scientists should continue to track the spread of SARS-CoV-2 in both humans and animals, as animal reservoirs of the virus could certainly pose a problem in the future, Chandran said.
Reduce the risk of problem variables
Is there anything we can do to reduce the risk of new problem variants emerging?
“What we need to do is reduce … the space in which the virus has to multiply. And the way we’re going to do that is by vaccinating people,” Chandran said. As of January 10, about 4.67 billion people worldwide had received at least one dose of a COVID-19 Vaccine, leaving nearly 40% of the world’s population completely unvaccinated, According to the New York Times.
Even if vaccines provide only partial protection against a future variant, as is the case with omicron, they are likely to reduce people’s chances of catching and transmitting the virus. However, vaccination would work best in combination with other measures, such as concealment, physical distancing and frequent testing, Chandran said. Most importantly, he noted, increasing the number of people vaccinated would relieve pressure on the health care system by preventing severe disease.
Early Evidence, posted Jan. 3 in the preprint database medRxiv, indicates that although the omicron variant can evade some of the antibodies induced by the vaccine, other immune defenses that the vaccine raises can still prevent severe infection. The study, which has not been peer-reviewed, showed that the vaccines generate “lasting responses” from helper T cells, which increase the body’s immune response upon sensing SARS-CoV-2, and killer T cells, which can kill infected cells. . The study found that these T cells exhibit cross-reactivity to both delta and omicron variants, meaning they can recognize and target both copies of the virus for destruction. Likewise, these T cells could provide protection against potentially worrisome future variants.
Overall, Mosman told Live Science, “As more and more people get infected and/or vaccinated, especially multiple times, they will build up higher levels of immunity, possibly against different variants.” “As this general level of immunity increases within the population, and around the world, the overall development of SARS-CoV-2 will likely decrease, and the epidemic will become endemic.”
This is how the pandemic could end – but we will likely encounter worrisome new variables until then.
Originally published on Live Science.
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