Table 1. Characteristics of laboratory-confirmed influenza A(H7N9) cases detected in 3 epidemic waves, China, 2013–2015.
| Characteristic | No. (%) cases |
|||
|---|---|---|---|---|
| Wave 1A, Jan 2013–Mar 2013, n = 19 | Wave 1B, Apr 2013–Sep 2013, n = 115 | Wave 2, Oct 2013–Sep 2014, n = 306 | Wave 3, Oct 2014–Mar 2015, n = 215 | |
| Age group, y | ||||
| 0–15 | 1 (5) | 6 (5) | 19 (6) | 17 (8) |
| 16–59 | 8 (42) | 47 (41) | 151 (49) | 113 (53) |
| 60–74 | 8 (42) | 37 (32) | 89 (29) | 58 (27) |
| >75 | 2 (11) | 25 (22) | 47 (15) | 27 (13) |
| Median |
60 |
61 |
57 |
56 |
| Male sex |
13 (68) |
81 (70) |
212 (69) |
154 (72) |
| Residence* | ||||
| Provincial capital or municipality | 10 (53) | 58 (50) | 57 (19) | 22 (10) |
| Other cities | 6 (32) | 23 (20) | 131 (43) | 100 (47) |
| Rural areas |
3 (16) |
34 (30) |
118 (39) |
93 (43) |
| Presence of ≥1 underlying medical condition† |
10 (53) |
42 (37) |
91 (30) |
64 (30) |
| Onset to hospital admission, d | ||||
| 0–2 | 2 (11) | 12 (10) | 41 (14) | 32 (18) |
| 3–6 | 8 (44) | 62 (54) | 151 (52) | 84 (46) |
|
>7 |
8 (44) |
41 (36) |
96 (33) |
65 (36) |
| Poultry exposure | ||||
| Any exposure to poultry | 15 (79) | 91 (83) | 165 (81) | 116 (74) |
| Occupational exposure to live poultry | 1 (5) | 6 (5) | 21 (7) | 22 (10) |
| Visited live poultry market | 12 (63) | 62 (54) | 132 (61) | 105 (67) |
| Exposure to sick or dead poultry | 0 (0) | 3 (3) | 3 (1) | 7 (5) |
| Exposure to backyard poultry | 6 (35) | 48 (49) | 34 (20) | 4 (2) |
*For more information, see the online Technical Appendix (http://wwwnc.cdc.gov/EID/article/22/6/15-1752-Techapp1.pdf). †Only underlying medical disorders associated with a high risk for influenza complications were counted here, including chronic respiratory disease, asthma, chronic cardiovascular disease, diabetes, chronic liver disease, chronic kidney disease, immunosuppressed status, and neuromuscular disorders.