When young, healthy persons are exposed to COVID-19, they can develop serious sickness for unknown causes. Genetic variations between individuals may produce severe responses to coronavirus infection, similar to those found with other infections such as influenza. Coronavirus and human genetics research could yield major results.
Large-scale studies employing modern DNA sequencing technologies could reveal the underlying reason, as well as aid in the design of treatment trials and the management of drug response.
Susceptibility to severe coronavirus symptoms is inherited.
When people have COVID-19, the majority of people only have mild symptoms, but a small percentage of people will have a severe or life-threatening reaction. While greater risk variables such as older age or existing health concerns can explain some of the difference, the reasons why some fit, young people become so unwell is one of the COVID-19 pandemic’s mysteries.
The human genome may hold some answers. The genome is the body’s instruction manual, including all of the data required to create, maintain, and repair a person. It can be found in practically every human cell. It’s made up of the DNA that we get from our parents.
Genes in the genome can act alone, but they usually perform in concert, like players in an orchestra. They also have interactions with their surroundings. In the presence of sunlight, for example, the activity of genes involved in skin protection against UV light damage increases.
Any two people’s genomes are around 99.9% identical; it’s the remaining 0.1 percent that distinguishes them. This variety could have a role in determining how different people react to different infections. When people are infected with coronavirus, for example, pieces of the virus are perceived by the immune system in different ways by different people. The result could be a shift in the immune system’s reaction to infection.
The human genome contains a large number of genes that play a role in the immune response to infection. Some are found on the X chromosome, which could explain why males (who only have one copy of the X chromosome) are more severely impacted by COVID-19 infection than females (who have two copies). Variations in human genomes, including immune system genes and others, may account for at least some of the variability in coronavirus infection responses. They could also explain why certain individuals respond differently to COVID-19 therapies.
Coronavirus research: sequencing and study of the genome
Although family or twin studies are helpful in determining whether an inherited element is likely to be driving a severe response to infection, identifying a few, or even a few hundred sets of letters that might be responsible among the genome’s six billion letters of code has been time-consuming and expensive until recently. It made prior attempts to look into the genomes of people who had severe reactions to infections like influenza during the 2009 pandemic challenging. 
Since the 2009 flu pandemic, however, there has been a revolution in both genome sequencing (‘reading’ each letter of the genetic code) and genome analytic techniques. This has made it easy to compare a large number of genomes in a short amount of time. High-speed computation has also made it easier to figure out how many genes operate together in response to infection, or, to use an orchestra example, which members of the orchestra are responsible for performing the melody.