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Hypothetical evolutionary pathway of avian influenza viruses of H13N2 (A) and H13N8 virus (B) subtypes isolated from black-tailed gulls in eastern China, 2016. Gene segments are colored according to their origin. Dashed virions indicate unidentified viruses. HA, hemagglutinin; M, matrix protein; NA, neuraminidase; NP, nucleoprotein; NS, nonstructural protein; PA, polymerase acidic protein; PB, polymerase basic protein.
