TABLE 2.

Prevalence of PA-343A/S and PA-347D/E

Host and subtype	No. of isolates analyzed	Prevalence (%) of the indicated amino acid at the following position in PA protein:
		343		347
		A	S	D	E
Human isolates
Seasonal H1N1	1,650	20.1a	0.2	99.5	0.06
H1N1pdm	7,578	93.2	0.05	99.9	0.01
H2N2	105	100	0	100	0
H2N2	9,714	7.4	92.6	99.9	0.04
Swine isolates
H1	3,293	95.1	0.9	95.7	3.6
H3	1,577	94.0	2.3	94.9	3.2
Other	88	94.3	1.1	100	0
Equine isolates
H3N8	128	60.1b	0	99.2	0
H7N7	12	58.3	41.7	100	0
Avian isolates
H1	822	99.4	0	100	0
H2	527	99.8	0	100	0
H3	2,140	99.2	0.8	99.95	0
H4	1,962	98.1	0.3	99.8	0
H5c	3,972	89.0	8.4d	99.7	0.2
H6	1,622	94.3	0.7	99.9	0.06
H7e	2,165	96.9	2.9f	99.9	0
H8	170	100	0	100	0
H9	2,164	89.7	9.1g	99.8	0.05
H10	1,099	87.2	12.6h	99.8	0.09
H11	653	99.4	0.3	100	0
H12	231	87.0	1.3	100	0
H13	395	94.7	5.3	100	0
H14	32	100	0	100	0
H15	17	100	0	100	0
H16	229	100	0	100	0
Avian and human H5	3,972	89.0	8.4d	99.7	0.2
Avian H5	3,717	89.0	8.6i	99.7	0.2
Human H5	255	88.6	5.5j	100	0
Avian and human H7N9	616	90.3	9.3	99.8	0
Avian H7N9	518	89.8	10.0	99.8	0
Human H7N9	98	92.9	5.1	100	0

^a79.6% of seasonal human H1N1 viruses encode E at this position.

^b39.8% of equine H3N8 viruses encode E at this position.

^cAvian and human isolates.

^dUntil 2010, 0.04%; since 2011, 21.5% (mostly from Vietnam and Cambodia).

^eAvian H7 viruses only; for human H7N9 viruses, see below.

^fUntil 2013, 0.2%; since 2014, 10.4% (almost all are H7N9 viruses).

^gUntil 2012, 1.5%; since 2013, 26.7% (mostly H9N2 viruses from China).

^hUntil 2012, 0.3%; since 2013, 40.5%.

ⁱUntil 2010, 0.04%; since 2011, 23.1%.

^jUntil 2010, 0%; since 2011, 43.8% (all are H5N1 viruses obtained from Cambodia in 2013).