subtypes

Influenza A virus

Influenza A virus, typically encountered more frequently than types B and C, and associated with the majority of serious epidemics, can be further subdivided into strains or subtypes based on antigenic differences in the external hemagglutinin proteins (H1-H16) and neuraminidase proteins (N1-N9). An open reading frame or ORF is a portion of an organism's genome which contains a sequence of bases that could potentially encode a protein. In a gene, ORFs are located between the start-code sequence (initiation codon) and the stop-code sequence (termination codon). Historically, human influenza virus infections have been associated with H1N1, H2N2, and H3N2 subtypes of…
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