Flu deaths are also linked to other morbidities Mike....but you are right, this really doesn’t address that. This addresses the question of what the real death rate is.
We have come at it from the perspective of identified Wuhan deaths. Trouble with that is some may have died while incidentally having the virus....others may have died outside hospitals from the virus and not been identified.
That said I have from the start believed the Diamond Princess is a good indication....everybody tested, 712 cases, 13 deaths. That is a 2% death rate in an old population in close quarters. If you fiddle with the age results that number is consistent with a 0.3% death rate in the general population.
The methodology used in the Economist approach is to infer the death rate by looking at divergences from the trend rate. This is the method used to estimate flu deaths and viewed in a focused time frame, should isolate other factors.
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Shark on the virus returning in winter....it hasn’t left yet and so far the effects of warmer weather are still uncertain. If that’s true it’s less seasonal than we think.
As for it becoming more deadly....hard to say. Some Italian doctors think it’s getting weaker and we are getting better at treating it:
‘ Doctors have observed that the coronavirus case-fatality rate seems to have decreased considerably since the early days of the pandemic. But a pre-publication study from Italian universities and local public-health authorities comparing the case-fatality rates in two provinces (Ferrara and Pescara) during March and April is the first to show this might be true.
After adjusting for age and comorbidities, the study found the overall death rate declined by some 40% from March to April with huge reductions in those over age 80 (from 36.3% to 16.1%), and subjects with hypertension (23% to 12.1%), diabetes (30.3% to 8.4%), cardiovascular disease (31.5% to 12.1%), COPD (29.7% to 11.4%) and renal disease (32.3% to 11.5%).’