This case defines the medical mystery baffling scientists.
This article noted: "Some people become infected but their immune systems spontaneously clear the virus, keeping them from developing the actual disease. These individuals may be asymptomatic, but this is not the same as resistance; an antibody test would generally detect evidence of a prior infection. Instead, resistance is broadly understood as having cleared a virus before it enters cells and gets a foothold - preventing infection, in other words, not just disease...
"A team of scientists at New York University and the Icahn School of Medicine at Mount Sinai were the first to report finding genes possibly tied to resistance to Covid-19. In early 2020, [a set of researchers] set out to sort through the potential genetic factors underlying Covid resistance. To do this, they used CRISPR genome editing technology to disable each of the 20,000 human genes in lung cells and then exposed them to SARS-CoV-2. Most of the cells died within a few days. 'Anything that lives is clearly missing something essential for a virus, and so potentially has a significant gene mutation, [said one of the researchers].'
"In January 2021, the group published a paper in Cell, reporting that RAB7A, a gene important for the movement of cargo from inside the cell to the cell surface, topped their quantitative ranking of genes the coronavirus can't do without. Inhibiting RAB7A reduces SARS-CoV-2 infection by ensuring ACE2 receptors are retained inside the cell, making them unavailable as the required point of attachment for the spike protein of SARS-CoV-2 (which attaches and then enters the cell)...
"In a paper accepted for publication in Nature Immunology, [several scientists] with the COVID Human Genetic Effort propose several potential sites in the genome that could govern resistance to SARS-CoV-2, and suggested undertaking large genome-wide association studies that screen large populations for gene variants associated with resistance to SARS-CoV-2..."
Another recent 2022 article is titled: "Are some people naturally Covid-proof? Scientists around the world are studying the phenomenon of health workers and others who are regularly exposed to the disease but have yet to become infected."
"Mounting evidence that people are naturally resistant to Covid and its mutations. One theory is that they have previously recovered from different coronaviruses...
"It's a common yet curious tale: a household hit by Covid, but one family member never tests positive or gets so much as a sniffle... Now scientists may have an answer: there is mounting evidence that some people are naturally Covid-resistant. For reasons not fully understood, it's thought that these people were already immune to the Covid virus, and they remain so even as it mutates. The phenomenon is now the subject of intense research across the world...
"In America and Brazil, researchers are looking at potential genetic variations that might make certain people impervious to the infection. And at University College London (UCL), scientists are studying blood samples from hundreds of healthcare staff who - seemingly against all odds - avoided catching the virus.
"One such frontline worker is Lisa Stockwell, a 34-year-old nurse from Somerset who worked in A&E and, for most of 2020, in a 'hot' admissions unit where Covid-infected patients were first assessed. Towards the end of last year she signed on with a nursing agency, which assigned her daily shifts almost exclusively on Covid wards. Colleagues working by her side have, at various points throughout the pandemic, 'dropped like flies'. But she says: 'I didn't get poorly at all, and my antibody test, which I took at the end of 2020, before I was vaccinated, was negative.
"'I expected to have a positive test at some stage, but it never came. I don't know whether I have a very robust immune system, but I'm just grateful not to have fallen sick.'
"Early on in the pandemic, Lisa's loved ones were also succumbing to the virus. She adds: 'My husband was sick for two weeks with a raging temperature that left him delirious.
"'Despite sharing a bed with him, I never caught it.
"'I even shared a car to work every day for two weeks with a nurse friend who, days later, was laid low with Covid...'
"She says: 'I was working every day on Covid wards, wearing PPE that was far from the best quality, and was initially terrified of catching the virus.
"'But I never did and now I'm beginning to think maybe I never will.'
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