TABLE 5.

Occurrence of the deletion in the NA stalk of influenza viruses^a

NA subtype or type	No. of NA sequences analyzed (no. of those with deletion found)
	Avian	Equine	Swine	Human	Chicken
N1b	1		2	17 (5)	1 (1)
N2	2		12	36 (1)	2 (2)
N3	1	1
N4
N5	1
N6	1
N7	1	2	1		2
N8	15	7
N9	3
NB				13
Total	25	10	15	66 (6)	5 (3)

^aThe 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. 

^bH5N1 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.