“There is no way to know 20% of COVID infectees require hospitalization until we know the number of infectees.”
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Those are confirmed cases, And as you noted, we have no way of knowing how many people aren’t infected. That’s getting into a “proving a negative” type of area.
“How much uncertainty is there in “20% of people who become infected with COVID will require hospitalization”?”
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I imagine you can just use “of all confirmed cases”, if you prefer, to be more semantically accurate. Doesn’t change the numbers, tho. ::shrug::
The projections being made use a set of assumptions. One of those is that 20% of people who become infected will require hospitalization.
My point is that assumption is pure speculation. It is not based on any facts at all. It is apples vs. oranges. We simply don't know. We lack the data and experience. Those will eventually accumulate.
The way I read those stats is about 3% of the tested population is infected. Other than that I have to speculate. I don't know if the 510 recovered/released from hospital + 67 deaths is all the 8,000 COVID positive people hospitalized. If it is, the hospitalization rate in South Korea is so far around 7%.