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Comment by elihu | Hacker News Reader

On the one hand, we don't know for sure if the number of virus particles one is exposed to correlates to severity of disease with SARS-CoV-2 in humans because we don't have rigorous studies that say so. On the other hand, it would be less surprising if it were true than if it isn't, and we should probably proceed on the assumption it's probably true. (Though I'm not an epidemiologist except to the extent that we've all become amateur epidemiologists these days, so don't take my word for it.)

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As I understand it, it's always better to be infected with few viruses than with many.

Think of it like this: I you get infected with 10 instead of 1.000.000 of a virus that grows x10 each day, your immune system has 5 extra days to fight it.

[Disclaimer: I'm a random software guy who reads a lot, not in any way a virus expert]

The problem with severe COVID, as I understand it, is an immune system that did nothing until it was too late, at which point it overreacts and releases a cytokine storm.

The hamster study did not show a big difference in outcome with higher viral load, contrary to what the article suggests.

If you trust in the science of conservation of energy you can release a iron ball on a pendulum from your nose and stand there waiting for the return, without taking a step back.

If you trust in the science of viral load not mattering, you will pick randomly when given the choice of having 1 or 5 novel viral particles placed in your nasal cavity. Nobody sane trusts that.

Yes, viral load is correlated with higher severity for majority of flu-like illnesses, supported by research. Even if this coronavirus is somehow different, combating viral load is still beneficial for avoiding viral viral co-infection (getting COVID-19 with severe influenza on top).

This was my take on the article as well: Masks = lower initial viral load, which seems logical to me. And, this doctor isn't saying anything much past "Wear a mask, dummy!" which I'm perfectly fine with.

I have a background in infectious disease research. From what I know, with this particular virus, it would be more surprising if the dose-severity dependence hypothesis was true than if it was not. There has been a lot of discussion of this hypothesis lately, but I am aware of exactly one experimental study that came anywhere close to proving it. That study dosed mice with a nasal titer ladder of flu and observed severity variations. Even that study failed to establish the dynamic range necessary to demonstrate dose dependence (the mice went from all survived to all dead in a single step of the titer IIRC).

There are certainly plausible mechanisms for the dose severity dependence hypothesis to be true, but with fast-replicating viruses I think the parsimonious assumption is transmission chains are dominated by a single event.

Not in COVID, but it's been demonstrated in other viruses. You can't do a challenge study with COVID, so the quality of evidence in COVID is going to be less.

https://www.latimes.com/california/story/2020-07-21/masks-he...

Variolation is much safer than being exposed to smallpox in the normal way:

https://en.m.wikipedia.org/wiki/Variolation

Even if it is true, it does not mean the difference is dramatic. The difference in the hamster study is minor.

It is possible that you need a minimum viral load to elicit an immune response at all and if so, the virus would first need to replicate to that level in vivo.

Those who don't wear mask should also get exposed to "low levels" of viruses but just abit further away than the mask wearers for the same exposure dose. Maybe people with mask are less likely to have bad health habits? E.g. people who dont put the seatbelt on also are worse drivers.

Sure, maybe I'd agree that they are people with masks are more likely to have good health habits, but I'd probably also assume that people with masks have worse health (even if they may have better habits).

I think their health is more relevant than habits in this case. I would guess that people who know they get sicker than most will be more cautious than average, they've been dealing with it their whole life. Maybe not totally independently of how their health habits are taught to them, but I bet a lot of it is just experience.

People know their bodies pretty well, even if they don't try very hard.

To me, it seems plausible that masks protect better against large droplets (that follow something like a parabolic trajectory) than small ones (that waft around in air currents).

https://www.thelancet.com/journals/lanres/article/PIIS2213-2...

Several other mammal species are susceptible to SARS-CoV-2. Has anyone tried doing a virus challenge study with animals?

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