> Various models and data sets put asymptomatic cases at between 20% and 50%. Those are fully asymptomatic - i.e. total end-to-end progression with either very mild symptoms indistinguishable from a minor cold, or no symptoms at all.
That's why I use South Korea as a model. They've tested enough that they should have found the majority of asymptomatic cases, and they still have CFR above 1% (1.7% as of this writing).
That also puts a bound on reasonable levels of occult spread. We can support maybe 50% of cases being totally asymptomatic and undetected, but if that is significantly greater then we'd see contact-tracing (again, SK-style) entirely fail as a control measure.
So it seems like an absolute best-case CFR is 0.5%, if it would be 1% among symptomatic cases and there again that many that never notice / are diagnosed with the disease. For the UK, that would give an optimistic projection of (66e6 * 50% * 0.5% =) 165k deaths in a "herd immunity" outcome with a "flat curve", so this is consistent with the range of your "hand-wavy estimate."
We will not know how effective testing has been until we have serological tests. There are a few assumptions being made regarding the efficacy of testing, and contact tracing will certainly miss pockets of asymptomatic people.
That's why I use South Korea as a model. They've tested enough that they should have found the majority of asymptomatic cases, and they still have CFR above 1% (1.7% as of this writing).
That also puts a bound on reasonable levels of occult spread. We can support maybe 50% of cases being totally asymptomatic and undetected, but if that is significantly greater then we'd see contact-tracing (again, SK-style) entirely fail as a control measure.
So it seems like an absolute best-case CFR is 0.5%, if it would be 1% among symptomatic cases and there again that many that never notice / are diagnosed with the disease. For the UK, that would give an optimistic projection of (66e6 * 50% * 0.5% =) 165k deaths in a "herd immunity" outcome with a "flat curve", so this is consistent with the range of your "hand-wavy estimate."