| Viruses | Description |
| Seasonal A (H1N1) | A/MISSISSIPPI/3/2001 wild-type virus (former seasonal H1N1; A/New Caledonia/20/99-like) - containing histidine at position 275 (275H) of the neuraminidase glycoprotein |
| Seasonal A (H1N1) (H275Y) | A/MISSISSIPPI/3/2001 variant virus (former seasonal H1N1; A/New Caledonia/20/99-like) - containing tyrosine at position 275 (275Y) of the neuraminidase glycoprotein―i.e. a H275Y substitution |
| Pandemic A (H1N1) | A/PERTH/265/2009 wild-type virus (H1N1pdm09; A/California/7/2009-like) - containing histidine at position 275 (275H) of the neuraminidase glycoprotein |
| Pandemic A (H1N1) (H275Y) | A/PERTH/261/2009 variant virus (H1N1pdm09; A/California/7/2009-like) - containing tyrosine at position 275 (275Y) of the neuraminidase glycoprotein―i.e. a H275Y substitution |
| Type B | B/PERTH/211/2001 wild-type virus (B/Sichuan/379/99-like) - containing aspartic acid at position 197 (197D) of the neuraminidase glycoprotein |
| Type B (D197E) | B/PERTH/211/2001 variant virus (B/Sichuan/379/99-like) - containing glutamic acid at position 197 (197E) of the neuraminidase glycoprotein―i.e. a D197E substitution |