Monday 27 July 2020

COVID

Viral load is apparently a big factor with COVID-19; how much initial exposure you have influences how bad you'll have it. Why? Wouldn't the virus duplicate in your cells, constantly growing anyway? Why does the initial dose matter so much?
The virus replicates exponentially, whereas your body fights it linearly.
To put numbers to it, suppose the following things:
  1. It takes 1 day for the virus to grow 10x.
  2. It takes your body 4 days to recognize a virus and begin to produce antibodies against it.
  3. Once your body starts producing antibodies, the virus stops replicating and your body produces enough to kill an additional 5,000 viral cells per day, i.e. 5,000 the first day, 10,000 the second day, etc.
So for Example 1, let's give you 1 virus.
The virus grows inside your body, unbeknownst to you, until 4 days in, when you start producing antibodies. At this point, the virus has grown 10x per day for 4 days, so there are now 10,000 virus cells infecting you. 5,000 die the first day, and then 5,000 die the second day, and then you're all better. Hell, you could've killed 10,000 that second day if you wanted to!
No sweat, right?
So what if you started with 10 viruses?
In this case, you end up with 100,000 virus cells when you begin to fight it on day 4. They can cause a hell of a lot more damage than 10,000, and it takes your body 6 days instead of 2 to fight them off. This will obviously be a much more severe illness.
All because of 9 extra viral cells.
I am not a doctor, a virologist, or anything approaching an expert. I don't even know if the question's premise is true, much less whether my answer is true.
But for whatever it's worth, that would be my guess from a purely mathematical point of view.

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