Table 4.

Homology of the gene segments of 1999 H9N2 influenza viruses with reference strain

Representative virusGene segment% Homologya with:
Qa/HK/G1/97 (H9N2)Dk/HK/Y280/97 (H9N2)Ck/HK/G9/97 (H9N2)HK/156/97 (H5N1)
Qa/HK/A17/99PB2 98.8 (98.9)85.6 (85.7) 97.4 (97.5) 97.8 (97.9)
PB1 99.2 (99.2)91.0 (90.8) 98.2 (98.1) 98.3 (98.3)
PA 98.7 (98.7)88.9 (88.9)88.4 (88.3) 97.4 (97.4)
HA 98.9 (98.7)90.1 (90.1)90.7 (90.7) —b
NP 99.1 (99.2) 88.7 (88.7)89.0 (89.1) 97.7 (97.8)
NA 99.2 (99.2)93.5 (93.4)93.1 (93.0)
M 99.3 (99.2)96.7 (96.6)96.5 (96.4) 99.2 (99.1)
NS 99.9 (99.9)93.7 (93.7)93.3 (93.3) 98.6 (98.6)
Ck/HK/FY20/99PB286.4 (86.0) 99.0 (98.5)86.3 (85.8)86.3 (86.0)
PB190.6 (90.7) 97.9 (97.8)90.8 (90.8)90.4 (90.4)
PA89.1 (89.1) 98.9 (98.3) 96.5 (96.7)88.7 (88.8)
HA89.4 (90.0) 98.5 (98.5) 96.5 (97.0)
NP89.2 (88.9) 98.5 (98.3) 98.2 (98.1)89.4 (89.1)
NA93.5 (93.2) 99.6 (98.8) 94.5 (94.2)
M95.9 (96.2) 99.0 (99.1) 98.5 (98.6)96.0 (96.3)
NS93.0 (93.1) 98.1 (97.8) 97.9 (97.6)93.5 (93.7)
  • a Calculated based on the nucleotide sequences of PB1 (nucleotides 988 to 2289), PB2 (67 to 1428), PA (19 to 1677), HA (88 to 1077), NP (34 to 1398), NA (20 to 1421), M (50 to 982), and NS (41 to 879). The highest homologies are in boldface. Values in parentheses are means for the five viruses shown in boldface in each group in Table 3 which were isolated in 1999.

  • b —, different HA or NA subtypes.