The daily number of deaths from COVID-19 in the US has not yet begun to increase following the dramatic surge in cases that began June 17. This chart from Oxford University shows that the cumulative case-fatality rate (CFR) in the US has been declining since about May 20, while it has not been declining in several other countries.
It seems that the chart shows a running CFR, since the cumulative CFR was higher than 6% in March and April and currently should be just under 6%. When the cursor is held at the end of the line for the US, a box pops up showing a CFR of 4.7 % for the United States on July 4.
I cannot find an account of how the running CFRs were calculated for the chart. Calculating an exact CFR at a point in time or for a limited period of time is tricky, because the dates that define the numerator do not define the denominator. click here.
Using a data set downloaded from ourworldindata.org, I have calculated a rough estimate of the CFR for the 30 days June 4 to July 3. The numerator is the number of deaths during that period and the denominator the number of cases reported for the period two weeks earlier, May 21 to June 19. The resulting current monthly CFR estimate is 3.41%. If the denominator period is three weeks earlier than the numerator period, the resulting estimate is 3.45%. I think that the calculations for the chart, however they were done, have given too high an estimate for the current US CFR.
Even if the CFR is and will remain below 4%, the number of deaths is likely to rise in coming weeks, as the denominator period catches up with the surge.
One reason for a falling case-fatality rate is expansion of the denominator, the number of confirmed cases, due to increased testing that picks up larger numbers of asymptomatic and mild cases. A related reason is a changing age pattern. Relatively young and healthy people who are contracting the illness from socializing in public places may account for a large proportion of new cases. The most important reason, however, may be improved medical care. Today, July 4, on MSNBC, Dr. Kavita Patel told Alex Witt that the chance of survival after admission to ICU had been one-fifth, and now it is four-fifths. I hope that the interview will be posted to msnbc.com, but it is not there yet .