Britannica Sources used in this answer

influenza - Classification of influenza viruses

What are the two major lineages of influenza B viruses?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Influenza virus — influenza A colored transmission electron micrograph showing influenza viruses (red) at the outer surface of a host cell.

The two major lineages of influenza B viruses are B/Yamagata and B/Victoria.1