Unlike influenza Type A, the B viruses are not broken down into subtypes, but can be broken down into lineage and strains. According to the CDC, the two B strains in circulation belong to either the B/Yamagata lineage or the B/Victoria lineage.
Influenza B is only found in humans and may be less severe than Type A, but it's still harmful. The Type B virus typically does not cause a pandemic.
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