[fiblye]

Before the vitamin D link was so widely reported, I remember seeing a bunch of comments online (including HN) from people saying things along the lines of "We've been self-isolating at home since January, only bought things online, and STILL got sick!"

I'm not a professional and this is just me spouting ideas, but I wonder if this is one reason why America is so hard hit compared to Asia. Americans generally commute by car, stay in a massive building complex all day for work, and go home and stay inside. In Asia, a huge proportion of people commute by foot, train (which involves walking to the station), or scooter. Then they walk to a grocery store or restaurant to get some food. I wonder if those minutes of continuous sun exposure add up and lighten the severity of it.

[nostromo]

That wouldn't account for places like Spain and Italy that are both sunny and more pedestrian friendly that were hit harder than the US though.

The theory that makes the most sense to me is that East Asia has had exposure to past viruses that were similar in nature but less lethal.

> Tatsuhiko Kodama of the University of Tokyo said preliminary studies show that Japanese people’s immune systems tend to react to the novel coronavirus as though they had previous exposure, and notes that there are centuries of history of coronaviruses emerging from East Asia.[1]

1. https://www.washingtonpost.com/world/researchers-ponder-why-...

[geomark]

Asia is a big place. In some densely populated areas in Asia most people live in bubbles, moving from air conditioned condos to taxis/subways to offices and then malls. They spend as little time as possible in the open due to pollution, weather and a cultural aversion to tanning. As a result, vitamin D deficiency is very common.

Some examples for Thailand are included in this paper[1]. One study said this: "Soontrapa et al. [15] evaluated vitamin D status in a younger group of premenopausal women found the prevalence of vitamin D insufficiency to be 77.8%, which was as high as the rate found in elderly Thai women living in nursing homes."

There is lots of sun in Thailand, but people avoid it as much as possible, staying indoors and applying lots of sunscreen if they must go out.

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5685050/

[aksss]

Is this where I say the obligatory reminder: "'Asia' is neither a country nor a culture."? ;)

[__oh_es]

Unfortunately by this logic I don’t think Italy and the UK would’ve had the same affect

[the_cat_kittles]

you can sanity-check your suspicion by looking at the data across countries. peru, spain, mexico and brazil should be enough to show that your idea is probably not correct

[fiblye]

Seems easy to rule out vitamin D if sunlight exposure isn't relevant at time of infection then.