Here's the Twitter thread from Trevor Bedford (head of the NextStrain project cited in your link) reviewing the work that discovered the spike protein mutation in the European strain that may affect transmissibility:
"Both Korber et al and our analysis show no measurable effect on patient outcome. Hence, the hypothesis at this point is entirely in terms of transmissibility rather than severity. 14/16"
The conclusion that mortality is higher comes from the higher death rates in European countries. However, there's a major confounder: when the epidemic exceeds testing capacity, only the most severe cases are tested and counted, and so the denominator in mortality rates (total cases) is inaccurately small. We know this is the case in much of Europe (and NYC): follow-up antibody tests put the number of total infections at ~10x the number of detected cases. That brings the mortality rate back in line with the ~0.5-1% that's been found in populations where everyone was tested.
So would your tendency at this point be to agree with Trevor that differences in tranmissibility are inconclusive? Or would you tend towards supporting the transmissibility hypotheses as long as there is some small amount of supporting evidence?
