Why is the COVID: BA.5 Omicron variant so contagious?

Despite cities and states relaxing mask requirements and allowing the state of emergency to expire, the United States is undoubtedly experiencing a surge in COVID-19 cases.

The rapid increase in cases is mainly due to A new subvariant of Omicron called BA.5.

Dr. David Wohl, a professor of medicine and infectious diseases at the University of North Carolina at Chapel Hill, explained how variants like BA.5 develop.

“Unlike humans, the virus makes a sloppy copy of itself, so baby viruses often look very different and are often flawed,” Wohl said. For some time, better mutants will emerge than other viruses. It is more likely to be transmitted from one person to another and is excellent in some way that helps it survive. “

Wohl added that the virus makes billions of copies, increasing the likelihood of more favorable mutants and accelerating the evolutionary process.

According to data from the Centers for Disease Control and Prevention, BA.5 is the most prevalent variant in the United States, rising from 17% of US cases a month ago to 65% last week. This variant spreads much faster than the previous variant. According to a news article from the science publication NatureInfects many people at once.

The number of people an infected person can infect with the virus is called the R0 (R-naught) value.Early COVID (popular in spring and summer 2020) R0 is about 2-3This means that anyone infected can infect a few others with the virus. The first couple strains of Omicron, the main cause of peak surges in cases last winter, 8-9 R0According to Dr. Wohl, it means that the infection rate was exponentially high.

BA.5 is even more contagious and is excellent at avoiding the power of the immune system.flat People who have been previously infected or have been vaccinated or boosted The virus test is positive. Dr. David Montefiori, a virologist at Duke University, says that people who had previously had a mild infection did not produce a strong immune response to the virus.

“Many people (almost half of those infected with this virus) do not have a very strong immune response when they recover. Their bodies do not have a strong immune response to the virus. It can be eliminated, “said Montefiori. “The difference in immunity between vaccines is not that great, so it’s good to get a vaccine. Unlike what you see in people who have recovered from an infection, most people have a good immune response to the vaccine. . “

Some experts BA.5 R0 is equal to or better than measles-Widely considered to be the most contagious virus with a known R0 value of 18-R0 envisions a fully susceptible population, and many at this point in the pandemic have some immunity. So the situation is simplified.

“R0 assumes that the population is vulnerable,” Wohl said. “Many people are less likely to be completely infected with BA.5, especially because they have been vaccinated and have been boosted, or because they have been infected with another variant that provides some protection. Probably as good as we are. There is no, but there is some protection. Again, there is a wall that the virus must jump over to infect a sufficient number of people, so R0 is now low, not 18. But it’s getting pretty expensive. Fewer people are taking steps to prevent or infect others. “

but New England Journal of Medicine Letter Montefiori suggests that the first vaccine and booster are more than 20 times less effective against BA.5 omicrons, especially for those who have not yet received the initial dose or booster. He said it was essential to receive it.

This is because the vaccine induces two branches of the immune system. First, the vaccine produces antibodies in a type of immune cell known as a B cell. This is a small torpedo that ignites a virus, more specifically a protein that the virus invades and interferes with. However, those antibodies declined over time.

However, another type of immune cell known as a T cell does not disappear. These are viruses such as SARS-CoV-2 (the virus that causes COVID-19) and fighter cells that prey on other invaders in the body.

“These killer cells are now working together with antibodies to control the virus and eliminate it from the body before it becomes a serious illness,” says Montefiori.

Wohl added that it is a mistake to think of vaccines in terms of absolute protection or no protection at all.

“They protect you from infection,” Wohl said. “Not as good as the previous variant, but with BA.5, the booster protects you. It’s not 100%, but you need some armor, even if it’s a tiny armor. There is no armor. “

Montefiori said the pandemic wasn’t over. COVID will be what we will live with for a very long time.

“Maybe forever,” said Montefiori. “We will see it evolve on a regular basis and there will be spikes.”

And both experts said that two simple actions can reduce an individual’s risk of becoming very ill or spreading the illness to other vulnerable people.

First, both said that wearing a mask indoors would prevent infection, especially for the elderly and people with immunodeficiency.

“This is a barrier method, and many people are working on barrier methods for a variety of infectious diseases,” Wohl said. “This is a barrier method to prevent the spread and acquisition of COVID-19.”

Wohl and Montefiori also recommend that people over the age of 50 get a second booster shot if they haven’t done so already.

“If you haven’t had a shot since January 1, it’s time for a shot,” Wohl said. “There is no downside, only the upside.”

Both added that BA.5 specific booster shots are expected by the fall, and anyone can safely shoot if they get another booster now.

“I hope it not only provides better efficacy for BA.5, but hopefully for future varieties,” Montefiori said. “We are now beginning to vaccine these other variants, which have mutations that contribute to the escape of the virus from immunity. The immune system recognizes these forms of the virus. I will attack. “

Meanwhile, both experts said they would wash their hands and continue to wear the mask.

“You may feel that COVID is over,” Wohl said. “But COVID is not done with us.”