Here’s a post from late February that enumerates 42 known strains of 2019-nCoV as a phylogenetic tree: https://nextstrain.org/narratives/ncov/sit-rep/2020-01-30?n=...

I’m a lay person here, but it seems a foregone conclusion that viruses experience frequent mutation, and that a novel virus infecting a new host species for the first time is going to see a relative explosion in mutations due to the extreme increase in the number of opportunities for it to occur.