There are two critical numbers that everyone wants to know: the true number of total Covid-19 cases, and the total number of deaths from the disease.
The ratio of the second to the first is the case fatality rate (CFR) or infection fatality rate (IFR) or sometimes it is called the case fatality risk. (It's not really a rate because there's no time involved).
This is a number that is famously hard to calculate (even for flu), especially because of uncertainty in the total number of cases. You can read more about it here, which is a review of the statistics for the 2009 influenza pandemic.
According to this, the CFR for 2009 was 4/1000 (0.45%). For the seasonal flu the statistic cited (I do not have a reference) is 1/1000 (0.1%).
The Diamond Princess cruise ship in Japan, which had 3,711 passengers, sustained 14 deaths in about 712 infected (tested by PCR). That's about 20 per thousand. But then you start with the arguments. Confined quarters, passenger population skewed older (median age 69). All but one who died were in their 70's (1 age was not released).
None of the 145 crew died (median age 36).
The CFR for the 1956-57 and 1968-69 flu pandemics was about 1/1000 (0.1%). What made them bad, of course (that word pandemic), was that no one on the planet had any immunity to those viral antigens.
People are arguing about the total number of cases. There's a lot of deliberate misinformation out there, because the true numbers look pretty bad. Officially, the US currently has 1M cases and 50K deaths, that's about 50/1000 (5%).
As a ballpark estimate we might guess the true number of cases is perhaps 10-fold higher. Serology testing is ongoing, but there is just no way that the number of cases in the US exceeds 5% of the population at this point, unless you believe Fox News (I don't).
However, we're also only counting half the deaths. Those adjustments (100K deaths and 10M cases) give a CFR of 10/1000 (1%).
So now the plan (since we have no choice at this point), is to try to resuscitate the economy, maintain a tolerable death rate, and wait for a vaccine. I think it's a reasonable hope (but just a hope) that an RNA vaccine will give tolerable protection and might be available in 6 months.
The safe plan (everyone stay inside until the vaccine) is just not tenable for the population as a whole, because even 2 months of this is going to cost (in the US) about 4 T dollars and 20% unemployment for a year at least.
Let's make some best-case assumptions. We suppose that with the right behavior, we can keep the number of cases over the next 6 months to 1/3 of the population (about half what would be needed for herd immunity). Suppose also that the CFR is 2.5/1000 (a very generous lower bound). So that's
(0.33 - 0.05) x 330M x 0.0025 = 230K
That's the rosy scenario. The worst case is ... the worst case.
So please just tell Jared Kushner to STFU.
Update 2020-05-02:
NYC reports 18,399 deaths
Total population 8,336,817
NY reports average 20% positive Ab in NYC
So that's a CFR of 18399/(0.2 * 8336817)
Too depressed to do the last step in the math.
