Table 2 |
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Characteristics and pathogenicity of influenza A viruses |
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| Viral features |
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| Number of HA subtypes |
16 |
| Number of NA subtypes |
9 |
| Predominant human subtypes |
H1, H2, H3 |
| Avian subtypes |
H1–H16 |
| HPAI subtypes |
H5 and H7 |
| Conversion to HPAI |
Basic amino acid insertion in HA |
| Avian sialic acid-galactose linkages |
α-2,3 linkages |
| Human sialic acid-galactose linkages |
α-2,6 linkages |
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HA, hemagglutinin; HPAI, highly pathogenic avian influenza; NA, neuroaminidase. |
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Sandrock and Kelly Critical Care 2007 11:209 doi:10.1186/cc5675 |
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