So originally the working theory was that the virus overwhelmingly targets older people and people with underlying health conditions. This is still mostly true, but more and more relatively young people with apparently no underlying issues are succumbing to COVID. Conversely, some people in their 80s and 90s recover, and most people have mild symptoms or are completely asymptomatic.
I know there aren’t really any answers for this yet, but I was wondering if any theories are forming. I’ll take opinion and speculation as well.
My complete layman’s guesses:
[ul]
[li]Amount of initial viral load. This SD post goes into it well.[/li][li]Unknown underlying conditions in seemingly healthy people that affects their immune response[/li][li]Genetics[/li][li]?[/li][/ul]
I believe this is a topic of current medical research, and you won’t find solid answers just yet. But I can throw some more speculation out there:
location of initial infection: I read somewhere that infections starting in the throat might have better outcomes than those that start in the lungs. (and some probably start in the gut, as well.)
Immune vitality prior to infection: In addition to age-related deterioration of immune response, sleep, exercise, general nutrition, and vitamins all contribute to a healthy immune system
How many of the receptors the virus targets do your cells have? Where are they most common in your body? This isn’t just genetic. I read something lat night speculating that one reason people with high blood pressure seem more susceptible may be that one of the drugs given to control blood pressure has as a side effect that people create more of the receptors the virus uses. (or it could go the other way, because the drug blocks the action of that receptor, and one reason people develop high blood pressure is more of those receptors and the drug helps. The article advised that at this time people should neither start nor stop that class of drugs due to SARS2. As I said, research is being done now.)
According to this some reasons could be that young people have fewer cytokines so are less likely to have a cytokine storm, but also because young people have been exposed to fewer coronaviruses (which cause a lot of colds), they have fewer antibodies which means fewer mismatched antibodies that can leave your body in a worse position to fight the virus.