Three future Covid-19 scenarios

The rapidly spreading omicron could make Covid-19 endemic, but there is also the risk that the virus will evolve further and become more dangerous to humans.

For nearly half a year, the Delta variant of nCoV has raged around the world, seemingly capable of defeating all other variants, to the extent that some scientists believe that the virus’ ability to infect humans has decreased. reach the limit.

However, the rise of Omicron in late November caused scientists to rethink. After being recorded in southern Africa, the new strain seems to quickly spread to dozens of countries around the globe in a very short time, prompting the World Health Organization to quickly list it as a dangerous variant. fear.

There are currently no complete data on the extent and virulence of Omicron, but preliminary studies in South Africa and several laboratories around the world suggest that this variant poses a higher risk of infection with Omicrons. people who have had Covid-19 in the past.

It is also believed to be better able to evade the vaccine than the parent strain. Preliminary research in South Africa showed that two shots of the Pfizer vaccine provided more than 90% protection against the original nCoV strain, but the effectiveness in preventing infection with the Omicron variant was only 33%. Even so, two doses of Pfizer vaccine still help prevent 70% of the risk of people infected with the Omicron strain being hospitalized.

As the studies gradually become published, scientists are wondering just how infectious the Omicron can be. The answer is not easy to find at this point, but researchers have outlined three scenarios for the future of Covid-19, the pandemic has infected more than 272 million people and more than 5.3 million people died in two years. via.

The first scenario that scientists think of is Covid-19 will become a seasonal disease under the influence of the strain Omicron spreads quickly but has signs of causing milder symptoms than other strains.

Viruses are simple life forms whose main goal is survival. Most scientists agree that the best way for nCoV to survive long-term is to become an endemic disease, similar to what influenza or other corona viruses do.

“The virus can’t seem to do any worse than what we’re dealing with,” said Vaughn Cooper, director of the Center for Medicine and Evolutionary Biology at the University of Pittsburgh, USA.

If the virus becomes dangerous and causes a higher mortality rate in infected people, it can experience a “hit his back” situation, because the host needs to live to be able to continue to transmit the pathogen to others. . Once the virus has reached its limit of transmissibility, future variants may not need to change how much it works.

“Are we going to have to play catch-up forever with nCoV? The answer is no. It will become a seasonally endemic disease. That could happen before the end of the decade,” Cooper said. .

Although there will be times when the virus outbreak is stronger than usual, this expert believes that vaccines will continue to be a tool to help people avoid the risk of serious illness.

According to him, antibodies provided by vaccines are not the only form of protection of the human body. White blood cells, commonly known as T cells and B cells, are also capable of remembering attackers for a longer period of time than antibodies.

“I can be confident that three doses of the current vaccine are enough to induce a diverse cellular immune response that will protect the vaccinated person against the virus for several years,” Cooper said. “I bet on that. I could get a virus, but it won’t get worse because T and B cells have faced something similar before.”

Medical staff take samples to test for Covid-19 at Sydney Airport, Australia on November 29.  Photo: Reuters.

Medical staff take samples to test for Covid-19 at Sydney Airport, Australia on November 29. Photo: Reuters.

However, some epidemiologists continue to draw up a second scenario, when the nCoV has reached its limit of transmissibility, because all the people it can infect have already reached immunity in the country. to some extent.

Until then, to continue to survive, the virus may have to find a way penetrate the human immune system, acquired after nCoV infection or vaccination.

“The easiest way for a virus to continue to cause a pandemic is to gradually avoid the immune system,” said Adam Kucharski, an epidemiologist at the London School of Hygiene and Tropical Medicine, UK. “This is similar to what we see with other seasonal coronaviruses.”

In that case, widespread immunity in the population could pressure the virus to evolve into new variants that further reduce the vaccine’s effectiveness.

“New strains that could potentially weaken vaccines are more likely to emerge,” warned Andrew Read, an expert on the evolution of infectious diseases at Pennsylvania State University in the US. “The virus has not yet unleashed its full mutant potential.”

Another scenario outlined by the scientific community is that as nCoV continues to spread, it will combined with other corona viruses on animals, forming a “hybrid strain” that returns to attack humans. Researchers warn that this is the worst scenario for humanity.

In this scenario, an animal that carries a different strain of corona virus could simultaneously be infected with Omicron or another variant of nCoV in humans. At that time, these two viruses will combine in the animal’s body, forming a hybrid strain that is much more dangerous than the old versions, and then infect humans again.

“We have a lot of coronaviruses in animals, so the possibility of a hybrid version appearing and infecting humans is very high,” said Read.

In the 21st century, humanity has recorded three types of corona virus causing serious illness that spread from animals to humans, including SARS-CoV, MERS-CoV and SARS-CoV-2 (nCoV). Read says the coronavirus is highly recombinant, and a study in May found this in a patient with pneumonia. Previously, a study in December 2020 also found a combination of corona virus in bats and pangolins.

Both Cooper and Read expressed concern about this risk in white-tailed deer in the United States. A study published by the National Academy of Sciences at the American University in late November showed that nCoV antibodies appeared in 40% of test samples of white-tailed deer in the states of Michigan, Pennsylvania, Illinois and New York from January to March. Another study also showed that 80% of samples tested on white-tailed deer in Iowa from November 2020 to January 2021 were positive for nCoV.

Such a high rate of nCoV infection makes researchers believe that white-tailed deer are very strong communicators of nCoV. They also identified different nCoV strains in this species, suggesting that they can be infected with the virus from humans.

“White-tailed deer appear almost everywhere in my neighborhood in suburban Pittsburgh,” Cooper said. “We know the virus is evolving in them, but how it evolves is a mystery.”

However, Cooper said that the possibility of a person or an animal being infected with two types of corona virus at the same time is extremely rare. “We should be worried about that, but the chances are pretty low,” he said, adding that the risk of the virus recombining is a rather remote concern.

“Most viral recombination fails, because their components don’t mix well,” Cooper said. “But one lesson we’ve learned from this pandemic is that anything unbelievable is possible.”

Thanh Tam (Follow Business Insider)

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