Here’s an article referencing a few recent empirical studies that have found lowered covid fatality rates since the beginning of the pandemic; that is, a reduction in the percentage of covid-infected people who die from the infection. Most persuasive are the studies that control statistically for age and comorbidities and that extrapolate beyond inpatients to population-wide estimates.
For the first months of the pandemic I estimated the US covid fatality rate at 0.6%; in mid-October, based on well-designed serology surveys, I raised it to 0.85%. Now I’m lowering back down to 0.7%, which is right around the IHME’s updated estimate.
Estimates of fatality and infection rates are cobbled together from multiple local studies available data. Population-based diagnostic testing surveys, repeated at regular intervals, would provide a more direct and accurate estimate. These surveys are still not being conducted in the US.
Reduced fatality rates are attributed to reduced overburdening of hospitals and to improved treatment. The current surge in cases is again starting to overload the healthcare providers and treatment facilities, so care might begin to deteriorate and fatality rates to go back up.