Alpha dominated in the US during April, May, and June. Delta has dominated since July 1.
Alpha and Delta cases in the US, April through December 2021: 24.2 million
US COVID-19 cases April through December 2020: 19.8 million
Alpha and Delta deaths in the US, April through December 2021: 272,259
US COVID-19 deaths April through December 2020: 341,746
The data is consistent with the theory that viruses mutate to become more infectious at the expense of lethality.
All indications so far indicate that this will also continue to be the case with Omicron.
