Difference between a coronavirus variant and strain - Los Angeles Times
▻https://www.latimes.com/science/story/2021-02-04/whats-difference-between-variant-strain-coronavirus
Pas de définitions strictes semble-t-il, mais lesdits « #variants » britannique (parce qu’il est plus contagieux) et sud-africain (parce qu’il échappe partiellement aux précédents anticorps) devraient plutôt être appelés « #souches. »
[...] a particular coronavirus specimen may contain one or more mutations that another specimen lacks. If there is no detectable functional difference, it is merely a variant.
However, if those mutations make the specimen more transmissible than its predecessors, or endow it with an added ability to evade a drug or vaccine, or alters it in another meaningful way, then it qualifies as a distinct strain.