Table 5.

Occurrence of the deletion in the NA stalk of influenza virusesa

NA subtype or typeNo. of NA sequences analyzed (no. of those with deletion found)
AvianEquineSwineHumanChicken
N1b 1217 (5)1 (1)
N221236 (1)2 (2)
N311
N4
N51
N61
N71212
N8157
N93
NB13
Total25101566 (6)5 (3)
  • a The NA amino acid sequences from the GenBank database were inspected for the presence of deletions in the stalk region of 10 or more amino acids.

  • b H5N1 strains from Hong Kong are not included. All 16 H5N1 isolates sequenced so far (7,41; the present study) contained the same 19-amino-acid deletion in the stalk.