Mutant strains of the novel coronavirus are spreading around the world.
This variant may be less susceptible to existing vaccines.
A broader term for any mutant organism or cell, not necessarily a strain; 変異株 emphasizes a distinct lineage or isolate.
Compound of 変異 (へんい, 'mutation') and 株 (かぶ, 'strain' or 'stock'). The term is a modern scientific coinage, likely influenced by English 'mutant strain'.