The COVID-19 fatality rates have been widely reported. The fatality rates are 5.8%, 5%, 3.6%, and 0.77% in Wuhan, Italy, the globe, and South Korea respectively. These fatality rates are concerning and the variability reported is also a bit confusing.
South Korea has done extensive testing (222,395 people) and their data presentation is excellent. The below table shows the number of cases (in the third colored column) by age along with the number of deaths (in the grey column with red text). The fatality rate varies depending upon age, from 0.12% for ages 30-39 to 7.2% for ages 80+. The mean age of those that died is ~73 years and 70% had preexisting health conditions.
Still, 0.12% seems concerning for ages 30-39. It’s ~10x the fatality rate of the flu, which is ~0.02% for ages 18-49. South Korea reports the details of every patient who died (I translated the table here). So, we can see that only one person between 30-39 died, a 35 year old male with a preexisting condition (liver disease). And even with South Korea’s extensive testing, it’s possible that many mild cases in this age band were still missed.
It’s important to recognize that South Korea’s fatality rate of 0.77% is a mixture of sub-populations with fatality rates that differ by ~two orders of magnitude (from ~0.1% to ~10%). Based upon this data, elderly with pre-existing health conditions are at higher risk and healthy < 50 years olds are at comparatively lower risk: there are two people < 50 years old who died of COVID-19 and both had preexisting health conditions.
That said, there is no perfect measure of the intrinsic lethality of the virus. Any measure of lethality is coupled to the actions taken. South Korea data is probably a good measure of COVID-19 lethality assuming a functional health system. In contrast, a poor response that floods the health system will probably drive up the number of deaths relative to what we saw in South Korea, as discussed here.
With this in mind, it would be instructive for the US and other counties to understand the actions that South Korea took in order achieve these statistics. This data cannot be viewed as an measure of intrinsic lethality or an inevitable outcome, but rather an outcome achieved through a specific set of coordinated government / state actions.