Making Sense of Medical Science (MSMS)

Why do some people who are infected with CoV-2 experience no, or mild, symptoms, while others become gravely ill? Age and underlying chronic conditions like heart disease, diabetes, obesity, etc. all seem to play a very significant role. But, since the pandemic began, stories of some healthy, young people without these risk factors becoming very sick have persisted as reported here and here and here. Why?

In this regard, this virus is very unusual and it becomes important to understand why some people just get a digestive or respiratory problem, other people suffer strokes, some get “COVID toes” (purplish toes), some lose their sense of taste and smell, some have systemic coagulopathies (clotting throughout their bodies), and others experience none of these symptoms. Are there different strains of the virus with different virulent properties, as was the case during the 1918-20 Spanish flu, or are there human genetic variables that cause these very different responses?

Popular genomics companies like 23andMe, Inc., and Ancestry, Inc., along with University investigators have been mining genomic databases to see if they can find human genetic links to help explain the disparate responses of individuals to the virus. Genome-wide association study (GWAS) that searched more than 750,000 genomes have found a genetic sequence on chromosome 9  in a region that determines blood type that correlates with disease severity. People with type O blood seem to be significantly protected from serious illness caused by CoV-2, while people with type A blood face a 50 percent greater risk of needing oxygen support or a ventilator should they become infected.

Another genetic association with disease severity was found on chromosome 3 and covers a cluster of six genes with potentially relevant functions. This stretch of the genome encodes a transporter protein known to interact with angiotensin converting enzyme 2 (ACE2), the cell surface molecule that allows the novel coronavirus to infect human cells. The region also encodes a collection of chemokine receptors, which play a role in the immune response in the airways of our lungs.

These statistically significant studies were reported by Andre Franke, a scientist at Christian-Albrecht-University, Kiel, Germany, along with Tom Karlsen, Oslo University Hospital Rikshospitalet, Norway.

How these genetic regions affect our response to the virus is not yet clear. More research needs to be done.

We will see.