Table 3 Comparison on positive rates of environmental surveillance for H7N9 virus, by three waves — Zhejiang Province, China, March 2013-February 2015

Towns, % (positive towns/total towns)

5.6 (5/90)

19.5 (69/354)

37.1 (104/280)

32.0 (161/503)

45.996

<0.001

Premises, % (positive premises/total premises)

2.8 (5/181)

11.0 (98/890)

28.2 (138/490)

16.0 (238/1488)

91.319

<0.001

Environmental samples of different premises, % (positive specimens/total specimens)

0.7 (11/1499)

4.3 (376/8647)

11.8 (481/4061)

6.1 (868/14207)

335.989

<0.001

 Live poultry markets

1.4 (7/511)

6.5 (374/5786)

15.1 (404/2669)

8.8 (785/8966)

203.645

<0.001

 Poultry rearing farms

0.7 (4/541)

0.2 (2/1263)

0.0 (0/489)

0.3 (6/2293)

5.558

0.029

 Concentrated areas of backyard poultry farms

0.0 (0/247)

0.0 (0/1074)

0.8 (2/250)

0.1 (2/1571)

6.302

0.049

 Slaughtering and processing plants

0.0 (0/17)

0.0 (0/141)

9.1 (17/186)

4.9 (17/344)

13.232

<0.001

 Habitats for migratory birds

0.0 (0/86)

0.0 (0/134)

0.0 (0/103)

0.0 (0/323)

-

-

 Others

0.0 (0/97)

0.0 (0/249)

15.9 (58/364)

8.2 (58/710)

48.346

<0.001

Environment samples of different types, % (positive specimens/total specimens)

0.7 (11/1499)

4.3 (376/8647)

11.8 (481/4061)

6.1 (868/14207)

335.989

<0.001

 Fecal dropping swab

0.3 (2/702)

2.8 (94/3306)

9.7 (174/1786)

4.7 (270/5794)

145.342

<0.001

 Poultry cage swabs

0.0 (0/315)

5.4 (106/1956)

11.3 (85/750)

6.3 (191/3021)

55.669

<0.001

 Drinking water samples

1.0 (2/201)

2.9 (27/943)

10.1 (34/338)

4.3 (63/1482)

31.962

<0.001

 Sewage from cleaning poultry

1.5 (1/67)

5.0 (43/859)

20.2 (61/302)

8.6 (105/1228)

62.802

<0.001

 Swabs of tables for slaughtering or processing poultry

1.6 (1/61)

7.3 (78/1063)

14.6 (93/636)

9.8 (172/1760)

28.542

<0.001

 Others

3.3 (5/153)

5.4 (28/520)

13.7 (34/249)

7.3 (67/922)

18.342

<0.001