Table 3.

Comparison of Influenza Virologic Surveillance by Birth Cohort, 2000–2001 Through 2016–2017 Seasons - Number of Specimens Tested and Percentage Positive for Influenza A

		Birth Cohort
		1918–1922		1933–1937		1947–1951		1957–1961		1968–1972		1977–1981		1985–1989
Season	Predominant Virus	Percent A Positive	Number of Specimens Tested	Percent A Positive	Number of Specimens Tested	Percent A Positive	Number of Specimens Tested	Percent A Positive	Number of Specimens Tested	Percent A Positive	Number of Specimens Tested	Percent A Positive	Number of Specimens Tested	Percent A Positive	Number of Specimens Tested
Prepandemic
2000–2001	H1	1.6	123	3.5	86	8.5	165	24.5	241	19.1	267	29.0	487	28.8	313
2001–2002	H3	30.8	221	34.4	122	30.0	207	32.5	268	34.1	279	45.0	518	37.2	462
2002–2003	H1	14.9	101	17.6	85	19.3	150	16.0	237	36.1	166	13.8	689	23.2	745
2003–2004	H3	31.9	238	41.9	179	31.6	250	32.2	311	42.7	457	44.1	726	43.9	1027
2004–2005	H3	38.1	307	43.3	215	41.7	345	41.3	380	47.0	406	35.0	488	31.4	608
2005–2006	H3	30.0	140	34.8	135	33.0	206	37.4	238	45.0	211	34.6	292	47.7	549
2006–2007	H1	18.1	127	19.6	102	24.8	165	30.0	230	40.0	260	35.1	288	28.8	781
2007–2008	H3	22.5	120	26.4	106	24.9	221	36.1	319	31.2	298	44.6	359	55.8	611
2008–2009	H1	4.7	86	16.2	99	22.6	146	41.0	212	41.8	220	44.1	286	35.3	595
Pandemic and Later
2009–2010	H1pdm09	4.0	1463	10.5	2621	21.2	4259	32.0	5566	31.1	4332	36.3	4854	46.3	6648
2010–2011	H3	37.4	1141	34.0	1505	29.4	1894	40.6	2239	39.4	1841	44.8	2241	44.6	3608
2011–2012	H3	31.8	912	27.6	1270	25.3	1555	27.3	1742	30.4	1616	36.5	1721	33.3	2233
2012–2013	H3	50.8	1963	43.1	3050	36.7	3170	33.8	3155	39.3	2650	43.1	2939	40.6	3368
2013–2014	H1pdm09	13.5	960	21.2	2563	31.1	3902	38.7	4517	41.7	3655	43.5	3796	41.5	4182
2014–2015	H3	56.2	2215	43.7	4794	34.2	4752	30.7	4276	29.6	3221	32.7	3487	34.0	4072
2015–2016	H1pdm09	7.6	631	14.0	2480	21.5	3421	26.9	3830	32.3	2765	30.2	2829	27.8	3257
2016–2017	H3	48.8	957	45.3	3450	41.0	3720	35.7	3542	33.5	2416	32.3	2476	34.5	2956