Scientists narrow down why some people keep avoiding Covid BA.5 could put an end to this happiness.

Most people in the US have had Covid-19 at least once – probably more than 70% of the country, Ashish Jha, White House Covid-19 response coordinator said on Thursday, citing data from the Centers for Disease Control and Prevention.

Many have been infected multiple times. in one form Study examining 257,000 US veterans who had contracted Covid at least once, 12% had been reinfected by April and about 1% had been infected three times or more.

This raises an obvious question: What is keeping this shrinking minority of people from getting sick?

Disease experts are focusing on a few predictive factors beyond individual behavior, including genetics, T-cell immunity, and the impact of inflammatory diseases such as allergies and asthma.

But even as experts learn more about why people are better off avoiding Covid, they warn that some of those defenses may not hold up against Omicron’s latest version, BA.5, which is remarkably good at spreading vaccine protection and bypass .

“It really takes two to tango,” said Neville Sanjana, a bioengineer at the New York Genome Center. “If you think about an infection and the bad things that happen afterward, it’s really a product of two different organisms: the virus and the human.”

Genetics could reduce Covid risk

In 2020 NYU researchers identified a variety of genes that could affect a person’s susceptibility to the coronavirus. In particular, they found that inhibiting certain genes that code for a receptor called ACE-2, which allows the virus to enter cells, could reduce the likelihood of infection.

Sanjana, who conducted this research, estimated that around 100 to 500 genes could affect susceptibility to Covid-19 in sites like the lungs or nasal cavity.

Genetics will “probably go a long way” in protecting against Covid-19, he said. “I would never say it’s the only contributor.”

In July, researchers identified a common genetic factor that could affect the severity of a coronavirus infection. in one to learn In more than 3,000 people, two genetic variations reduced expression of a gene called OAS1, which is part of the innate immune response to viral infections. That was associated with an increased risk of Covid-19 hospitalization.

So increasing gene expression should have the opposite effect – reducing the risk of serious illness – although it wouldn’t necessarily prevent infection entirely.

“It’s natural to get infected once you’re exposed. There is no panacea for this. But how you will respond to that infection after infection is affected by your genetic variants,” said Ludmila Prokunina-Olsson, lead investigator on the study and head of the Laboratory of Translational Genomics at the National Cancer Institute.

Still, Benjamin tenOever, a microbiology professor at NYU Grossman School of Medicine who helped conduct the 2020 research, said it will be difficult for scientists to pinpoint a specific gene responsible for preventing Covid infection.

“While there certainly could still be some genetics that make people completely resistant, they will be incredibly difficult to find,” tenOever said. “People have been searching extensively for two years with no real results.”

T cells could remember previous encounters with coronaviruses

Aside from this new coronavirus, SARS-CoV-2, four other coronaviruses commonly infect humans and typically cause mild to moderate upper respiratory illness like the common cold.

A Recent study suggested that repeated exposure to, or occasional infection with, these common cold coronaviruses might confer some protection against SARS-CoV-2.

The researchers found that T cells, a type of white blood cell that recognizes and fights off invaders, appear to recognize SARS-CoV-2 based on previous exposure to other coronaviruses. So if a person infected with a common cold coronavirus is later exposed to SARS-CoV-2, they may not get as sick.

But that T-cell memory is unlikely to completely prevent Covid.

“While neutralizing antibodies are key to preventing infection, T cells are key to terminating infection and modulating infection severity,” said Alessandro Sette, study author and professor at the La Jolla Institute for Immunology .

Sette said it’s possible that some people’s T cells clear the virus so quickly that the person never tests positive for Covid. But researchers aren’t sure yet if that’s going to happen.

“It’s possible that despite the negative test, it was a very failed, transient infection that went undetected,” Sette said.

At a minimum, T cells from previous Covid infections or vaccines should continue to provide some protection against coronavirus variants, including BA.5.

Allergies may add a little extra protection

Although asthma was considered a potential risk factor for severe Covid earlier in the pandemic, recent research suggests that low-level inflammation from conditions such as allergies or asthma may have a protective benefit.

“You will hear these stories about some people who are getting sick and have full blown symptoms of Covid and during that time have slept next to their partner for a whole week without giving it to them. People think they must have genetic resistance to [but] A big part of this could be that the partner next to you has in some way a greater than normal inflammatory response in the lungs,” tenOever said.

A study may found that a food allergy halved the risk of coronavirus infection in nearly 1,400 US households. Asthma did not reduce the risk of infection in the study, but it did not increase it either.

One theory, the researchers say, is that people with food allergies express fewer ACE2 receptors on the surface of their airway cells, making it harder for the virus to enter.

“Because there are fewer receptors, you either have a much weaker infection or you’re less likely to even become infected,” said Tina Hartert, professor of medicine and pediatrics at Vanderbilt University School of Medicine, who co-led this research.

The study took place from May 2020 to February 2021, before the omicron variant emerged. But Hartert said BA.5 probably wouldn’t eliminate cross-protection from allergies.

“If something like allergic inflammation is protective, I think that would apply to all variants,” Hartert said. “The degree to which it could be protective could certainly be different.”

Avoiding infection is more difficult with BA.5

For many, the first explanation that comes to mind when they think of Covid avoidance is personal caution. tenOever believes that individual behavior, more than genetics or T cells, is the key factor. He and his family in New York City are among those who have never had Covid, which he attributes to precautions like staying home and wearing masks.

“I don’t think for a second that we have anything special in our genetics that makes us resilient,” he said.

It is now common knowledge that prior to Omicron, Covid was more preventable, back when a small percentage of those infected accounted for most of the spread of the virus. A Study 2020found, for example, that 10-20% of infected people accounted for 80% of transmission.

But omicron and its subvariants have made any social interaction riskier for everyone involved.

“The Omicron variants are probably far more equal than the earlier variants,” said tenOever.

BA.5 in particular has increased the likelihood of people who have previously avoided Covid getting sick. President Joe Biden is a prime example: He tested positive for the first time this week.

Still, Jha said Thursday, “I don’t think every American will be infected.” Scientists narrow down why some people keep avoiding Covid BA.5 could put an end to this happiness.

Fry Electronics Team

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