How have some people avoided getting Covid-19?
How have some people avoided getting Covid-19?

How have some people avoided getting Covid-19?

Dozens of Britons have had four seizures of Covid-19, and thousands more have been infected three times, according to official data.

When the pandemic entered a third year, numbers from The UK Health Safety Agency (UKHSA) showed that 62 people had reported four positives Covid testeach at least 90 days apart.

But while many people have been re-infected several times, others seem to have avoided getting coronavirus despite coming into close contact with cases – a difference that scientists have struggled to explain. Here are some of the more plausible theories.

Genetic resistance

An international consortium of researchers has launched a study to investigate whether a small proportion of humans may be genetically resistant to Covid-19. Identifying such protective genes may lead to the development of new treatments for coronavirus.

The researchers made a global appeal in October last year to find apparently Covid-resistant individuals to participate in the study with the goal of recruiting a total of at least 1,000. “Of particular interest are people who shared a home and bed with an infected partner – couples known as dissenting couples,” a scientific journal reported Nature.

The team, from ten research centers worldwide, had already recruited about 500 potential candidates. And within two weeks of launching their hunt, another 600 people had reportedly stepped forward and offered to sign up.

“I did not believe for a second that people themselves, vulnerable and apparently not infected, would contact us,” said study co-author Jean-Laurent Casanova of Rockefeller University in New York.

The possible resistance that study participants may have “is known to exist for other diseases, including HIV, malaria and norovirus”. The GuardianIt reported science correspondent Linda Geddes.

“In these cases, a genetic defect means that some people lack a receptor used by the pathogen to penetrate cells so they cannot become infected,” Geddes explained.

Supervisor AndrĂ¡s Spaan, professor at Rockefeller University in New York said that “it could well be that in some individuals there is such a defect in a receptor used by Sars-CoV-2”, the virus that causes Covid-19.

Spaan “believes, however, that the majority of those who have avoided Covid are unlikely to be genetically resistant, even though they have partial immune protection,” Geddes said.

Common cold theory

A study led by a team from Imperial College London found that people who have fought the common cold may have a lower risk of getting Covid-19.

“We found that high levels of pre-existing T cells, created by the body when infected with other human coronaviruses such as the common cold, can protect against Covid-19 infection,” said study co-author Rhia Kundu of Imperial’s National Heart. and Lung Institute.

The researchers tested blood taken from 52 people in September 2020 – before Covid vaccines were rolled out – who lived with others who had just been tested positive for coronavirus. A total of 26 Covid received during the 28-day study period.

In an attempt to determine why the other half of the group escaped infection, the researchers looked at the role that T cells played, which is “a crucial part of the body’s immune system”, said BBC.

Some of these T cells “kill all cells infected with a specific threat,” such as a cold virus, the television station explained. And after a cold infection, “some remain in the body like a memory bank, ready to defend against future attacks” from the virus.

According to a study published in Nature in January, the 26 subjects who did not receive Covid had “significantly higher levels” of pre-existing T cells induced by previously common cold coronavirus infections, which also recognize proteins from the Sars-CoV-2 virus.

However, co-author of the study Kundu stressed that “no one should rely on this alone”, adding: “The best way to protect yourself from Covid-19 is to be fully vaccinated, including getting your booster dose.”

The team and other scientists also pointed out that not all colds are coronavirus. Dr. Simon Clarke of the University of Reading, who was not involved in the study, said: “It could be a serious mistake to think that anyone who has recently had a cold is protected against Covid-19, as coronavirus only accounts for 10 % -15% of colds. “

Blood type compound

Some research results have suggested that people with blood types A and AB are more susceptible to getting Covid, while those with blood type O are less likely to test positive for the virus.

Two studies published in Blood progress journal in October 2020 showed a possible link between blood type and vulnerability to Covid. The first, by Danish researcherscompared health registry data from more than 473,000 individuals tested for Covid-19 with data from a control group of more than 2.2 million untested individuals.

“Among the Covid-19 positives, they found fewer people with blood type O and more people with A, B and AB types,” reported Science Daily.

That second study looked at data from 95 critically ill Covid patients admitted to Vancouver, Canada. Patients with blood types A and AB were found to be more likely to require mechanical ventilation and require dialysis for renal failure.

Despite these findings, however, many scientists have remained unconvinced about the alleged blood type compound. A review of nearly 108,000 Covid patients in the United States, outlined in a paper in Journal of the American Medical Association in April 2021 found no such connection and said more research was needed.

Asymptomatic infections

A less scientifically possible explanation for why some people appear to have avoided Covid is that they have actually been infected but did not show symptoms.

According to ReutersGovernment estimates of the proportion of asymptomatic Omicron infections in the UK have ranged from 25% to 54%.

And while many people have continued to test for Covid routinely, a recent study by Imperial College London found that lateral flow tests may be missing a “significant” number of infections.

An analysis conducted by a team from the university showed that the Innova brand’s test was missing between 20% and 81% of the positive cases.

Concerns have also been raised that many people who do such tests make mistakes – such as eating or drinking within half an hour in advance, or forgetting to brush their noses in advance – which can cause incorrect results.

Like a Twitter user asked, “Anyone else wondering if they’re really testing negative or just not pushing that thing far enough up their noses?”

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