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Comment by stanski | Hacker News Reader

If a lot of the damage is often caused by an overreacting immune system, why isn't this disease harder on younger people who presumably have stronger immune systems? Kind of like the Spanish flu? This doesn't add up for me and this article doesn't dwell on that either.

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There is still no proof for this but some scientists suggest people over 80 years old came in contact with a similar virus when they were young and now their immune system is overreacting (like when the second sting of a wasp can be much worst that the first).

In the Netherlands they found out by coincidence that some people who have a broken TLR7 gene don't fight the virus so the virus hits them very hard.

So there may be multiple reasons.

The issue with young people and the Spanish flu wasn’t “they have stronger immune systems so they cytokine storm harder and die in greater rates”, it was that there was an earlier endemic flu like 40 years before and basically everyone over like ~40 had been exposed to it and they had immunity, and anyone under that age had not been exposed so they lacked immunity.

I've seen the idea of cross-reactivity and T-cell immunity being passed around.

I think the idea is that younger, healthier people with better immune systems are able to prevent the virus from replicating as much, whereas sluggish immune systems and bodies that are highly inflamed like overweight ppl, diabetics, etc. (high leptin, also related to il-6) get overwhelmed.

T-cell immunity/cross-reactivity meaning that most people have the ability to fight the virus from exposure to other coronaviruses.

I think a major component of the death toll from the pandemic is basically a consequence of obesity. I'm suspicious that govt interventions, planning, etc make that much difference when the US is an order of magnitude more obese than Japan, for example.

That hasn't really been seen in the data though. Yes, obesity has been linked to more severe cases, but some of the hardest hit, highest mortality rate areas, like NYC and Italy, are markedly lower in their rates of obesity that other areas with lower mortality rates.

The article suggests a lack of ACE2 cell receptors in young people could contribute why the disease isn't as hard on them.

That's for the very young, ie children, at least from what I gathered.

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