The moment a preprint emerges describing a new patient isolate of SARS-CoV-2, with a change in the genome sequence, the world seems to explode with concern about a new viral ‘strain’. I want to explain why such angst is misguided and in the process explain exactly what is a virus strain and a virus isolate. In science, word usage matters. And sadly, even virologists often do not use their terms properly. I’ve written about it before.