Recent research indicates that different strains of the novel coronavirus SARS-CoV-2 do indeed have meaningful differences in pathogenicity.

This was difficult to confirm previously.

SCMP summary article:
https://www.scmp.com/news/china/science/article/3080771/coronavirus-mutations-affect-deadliness-strains-chinese-study

Original preprint:
https://www.medrxiv.org/content/10.1101/2020.04.14.20060160v1

The extent to which strain virulence differences may explain regional variation in case growth and outcomes is not yet clear, but it is very suggestive.

Another useful implication: https://twitter.com/Pharmaheretic/status/1252382829335293952?s=20