[BostonCard]

I think it's because of loose use of language.  I myself have referred to them as viral "strains", but as the virologist makes clear, different strains should have measureably different properties, not merely genetic differences.

Uptodate simply refers to them as two different types of virus:

In a phylogenetic analysis of 103 strains of SARS-CoV-2 from China, two different types of SARS-CoV-2 were identified, designated type L (accounting for 70 percent of the strains) and type S (accounting for 30 percent) [9]. The L type predominated during the early days of the epidemic in China, but accounted for a lower proportion of strains outside of Wuhan than in Wuhan. The clinical implications of these findings are uncertain.

BC

[BostonCard]

I think it's because of loose use of language.  I myself have referred to them as viral "strains", but as the virologist makes clear, different strains should have measureably different properties, not merely genetic differences.

Uptodate simply refers to them as two different types of virus:

In a phylogenetic analysis of 103 strains of SARS-CoV-2 from China, two different types of SARS-CoV-2 were identified, designated type L (accounting for 70 percent of the strains) and type S (accounting for 30 percent) [9]. The L type predominated during the early days of the epidemic in China, but accounted for a lower proportion of strains outside of Wuhan than in Wuhan. The clinical implications of these findings are uncertain.

BC