Table 3.

Seroprevalences of antibodies (HI titer ≥80 and ≥160) to H9N2 virus in poultry workers, swine workers, and the general population in four cross‐sectional surveys in 2013, 2014, 2015, and 2016

Characteristic/Period	Nov 2014				Apr 2014				Apr 2015				Apr 2016
	HI titer ≥80		HI titer ≥160		HI titer ≥80		HI titer ≥160		HI titer ≥80		HI titer ≥160		HI titer ≥80		HI titer ≥160
	N. (%)	P value	N. (%)	P value	N. (%)	P value	N. (%)	P value	N. (%)	P value	N. (%)	P value	N. (%)	P value	N. (%)	P value
All participants
Participant category	30 (0.79)		5 (0.13)		45 (1.29)		14 (0.40)		20 (0.61)		5 (0.15)		27 (1.22)		10 (0.45)
Poultry workers	6 (0.48)	0.017	1 (0.08)	0.631b	17 (1.61)	0.531	3 (0.28)	0.473b	13 (1.16)	0.005	3 (0.27)	0.245b	19 (2.77)	＜0.001	7 (1.02)	0.003b
Swine workers	18 (1.35)		3 (0.23)		14 (1.12)		4 (0.32)		6 (0.60)		2 (0.2)		5 (0.82)		3 (0.49)
General population	6 (0.50)		1 (0.08)		14 (1.18)		7 (0.59)		1 (0.09)		0 (0)		3 (0.33)		0 (0)
Gendera
Male	19 (0.98)	0.176	2 (0.10)	0.681b	25 (1.48)	0.325	7 (0.42)	0.897	7 (0.44)	0.208	1 (0.06)	0.375b	13 (1.22)	0.847	6 (0.56)	0.327b
Female	11 (0.59)		3 (0.16)		20 (1.11)		7 (0.39)		13 (0.78)		4 (0.24)		13 (1.14)		3 (0.26)
Age groupa
≤39	6 (0.48)	0.266	1 (0.08)	0.858b	12 (1.07)	0.056	5 (0.45)	0.679b	8 (0.78)	0.687	1 (0.10)	0.513b	5 (0.90)	0.515	3 (0.54)	0.768b
40‐59	17 (0.88)		3 (0.16)		19 (1.08)		8 (0.45)		8 (0.51)		2 (0.13)		13 (1.17)		4 (0.36)
≥60	7 (1.14)		1 (0.16)		14 (2.28)		1 (0.16)		4 (0.62)		2 (0.31)		9 (1.66)		3 (0.55)
Presence of at least one chronic disease
Yes	3 (1.06)	0.489b	1 (0.35)	0.323b	4 (2.26)	0.286b	0 (0.00)	1.000b	0 (0.00)	0.250b	0 (0.00)	1.000b	1 (0.48)	0.507b	1 (0.48)
No	27 (0.77)		4 (0.11)		41 (1.23)		14 (0.42)		20 (0.67)		5 (0.17)		26 (1.30)		9 (0.45)	1.000b

^aVariables have missing data.

^bUsing Fisher's exact test.