Table 1.

Number of Cases of Influenza-Like Illness (ILI) and Influenza Virus–Positive Specimens, by Virus Subtype, Shenzhen, China, 1995–2009

Year	URI or ILI Cases,No. (%a)	Specimens,No.	Positive Specimens, No. (%)	Influenza A Virus Subtype Positivity			B Positivity,Proportion (%)
				H3N2, No.	H1N1, No.	Overall, Proportion (%)
1995	37 509 (54)	352	16 (5)	7	1	8/16 (50)	8/16 (50)
1996	51 500 (79)	241	33 (14)	17	11	28/33 (85)	5/33 (15)
1997	50 294 (71)	608	34 (6)	2	5	7/34 (21)	27/34 (79)
1998	90 063 (71)	2300	40 (0.2)	39	0	39/40 (98)	1/40 (2)
1999	89 362 (72)	1187	70 (9)	36	0	36/70 (51)	34/70 (49)
2000	49 836 (75)	1509	40 (3)	10	11	21/40 (53)	19/40 (47)
2001	51 393 (75)	1168	74 (6)	1	50	51/74 (69)	23/74 (31)
2002	156 491 (68)	815	34 (4)	12	0	12/34 (35)	22/34 (65)
2003	27 268 (8)	779	45 (6)	41	0	41/45 (91)	4/45 (9)
2004	29 658 (7)	773	20 (3)	9	0	9/20 (35)	17/20 (65)
2005	25 097 (5)	2325	133 (6)b	33	51	84/133 (63)	22/133 (17)
2006	112 651 (6)	2486	154 (6)	3	103	106/154 (69)	48/154 (31)
2007	153 749 (7)	2526	290 (11)	172	11	183/290 (63)	108/290 (37)
2008	158 849 (6)	3183	389 (12)	48	177	225/389 (58)	164/389 (42)
2009	221 552 (7)	5125	1306 (25)	479	122; 450c	1051/1306 (80)	255/1306 (20)
Overall	1 305 272	25377	2678	903	991	1894/2678 (71)	757/2678 (28)

Abbreviation: B, influenza B virus.

^a Data indicate the proportion of visits for upper respiratory infection (URI) or ILI among all consultations. URI visits were monitored during 1995–2002 in Shenzhen, whereas ILI visits were monitored during 2003–2009.

^b A total of 27 isolates in 2005 were not subtyped.

^c In 2009, 122 H1N1 isolates were seasonal strains, while 450 of these isolates were the novel 2009 pandemic influenza virus A subtype H1N1 strain.