I've heard that as well. Basically, the spread of the virus inside your body is exponential too, whereas the immune system's response time will be fairly static. So if you're exposed to a little, the immune system has time to respond before the infection gets out of control; if you're exposed to a large amount, by the time the immune system starts to respond, the virus is already widespread in your system.
Interesting - almost identical to the idea of not overwhelming relatively inflexible health services with spikes of new cases, only within a single human body?
Why wouldn't it be the other way around? If the virus replicates very fast, people with minimum infectious doses have a couple replication generations of extra time.
If the virus replicates more slowly, a large infectious dose would have the same impact as multiple replication generations.
I'm not asserting the above is what happens, I'm asking the question.
If it were 'less' exponential, and each cell only infected, say, 5 others, then you get to 500x late in the 4th generation.
In a cartoon example where a low exposure leads to 1 infected cell and a high exposure leads to 500 infected cells, the low exposure matters more if the reproductive factor is lower.
There is an interesting accidental study about this regarding norovirus. (Back in 2014 I think, not the 2017 Tennessee thanksgiving event)
Some guy vomited in a restaurant. Then you can clearly model the time from exposure to symptoms in everyone else based on how far away they were when the guy vomited. Though in this case the viral exposure was very high for everyone in the restaurant.
That's a theory I've heard before. I don't remember where, unfortunately. Does anyone have a source?
The basic theory is that if you catch the virus, you want to have it in your nose first so your body has time to start a response before it reaches your lungs.
If you get a large dose into your lungs at the start (perhaps because you work at a hospital with insufficient PPE) it's less likely to be mild.
> The basic theory is that if you catch the virus, you want to have it in your nose first so your body has time to start a response before it reaches your lungs.
That's a thought that has crossed my mind before: if it's better the farther up in the respiratory system the initial infection happens, then all that hand washing might be a bad idea, at least for the personal outcome. It depends a lot on wether you expect the full wave to eventually roll through until herd immunity or if you expect it to be stopped early, either by continued distancing until it's starved our by a vaccine.
>That's a thought that has crossed my mind before: if it's better the farther up in the respiratory system the initial infection happens, then all that hand washing might be a bad idea, at least for the personal outcome.
Huh? How does that figure? Hand washing will means less (or no) virii in your nose/mouth.
So, isn't it (a) good in itself, and (b) totally orthogonal to the infection happening "farther up in the respiratory system" (aside the positive, that if it happens and is further up, it will also be less viral content)
> Huh? How does that figure? Hand washing will means less (or no) virii in your nose/mouth.
If you make "first contact" by inhaling tiny droplets it's possible that they will make landfall right down in the lungs, whereas an infection from dirty fingers is guaranteed to start in the nose/mouth area and will already be an immune system project while it works it's way deeper down. Still worse than not getting infected at all, but if you assume that it will eventually hit you anyways, easing into the infection via the nose would surely be preferable to starting in the lungs where it's actually dangerous.
The reverse of this would be accumulating an infective dose from the leakage amount allowed through by PPE while working in extreme exposure. I doubt that there is empirical data regarding viruses, but everything we've learned about particulate emissions suggests that smaller particles reach deeper into the lungs. So it seems quite convincing to me that people who do fall ill despite PPE fall ill harder. Might explain the prominent medical worker deaths.