severe acute respiratory syndrome coronavirus two also called SARS-2, is the virus that causes COVID-19. So these are

different things, even if they're often used interchangeably. The former is the virus. The latter is the

disease caused by the virus. But the virus that causes the COVID-19 disease has, like every other virus, mutated to get where it is today.

Just like other sorts of life, from bacteria to turtles to humans, viruses evolve in usually tiny ways from generation to generation, and because their

generational progress is rapid by human timescales, that means they evolve fairly quickly,

from our perspective. Us being a species that has decades-long generations, rather than

generations that basically shift every time

a new host is infected. Because of this tendency of life to rearrange genetic information in small

or occasionally somewhat dramatic ways, in order to better compete and continue to pass on their genes,

life also tends to iterate and shift and mutate, though the terminology on this can also sometimes be a bit opaque and misunderstood.

Case in point, a disease variant is a genetic variation of a main strain. So it's distinct enough to be

differentiated from other variants, but not so different that it has become its own strain yet,

which requires substantially more differentiation, and which typically arises when members of a species are genetically separated

from each other, evolving after that division in accordance with very different environmental

pressures.

That said, the concepts of strain and variant are artificial, in the sense that we kind of just made them up to help us

organize the world a bit better and to help us more concisely explain degrees of relatedness.

So basically different strains means a big bundle of differences between organisms with

shared ancestors and variants have more in common,

but are distinct enough to have become their own thing, even if they're not yet distinct strains.

Until recently, COVID cases caused by variants were labeled with a collection of different

nomenclatures, depending on where

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