Table 2. Characteristics of 613 index case-patients with pandemic (H1N1) 2009 and their close contacts, Beijing, China*.
| Characteristic | No. (%) |
|---|---|
| Index case-patients | |
| Female sex | 265 (43.2) |
| Locally acquired cases | 230 (37.5) |
| Subclinical infection | 12 (2.0) |
| Infected close contacts |
110 (17.9) |
| Close contacts, n = 7,099 | |
| Female sex† | 3,514 (50.0) |
| Relationship to index case-patient | |
| Spouse | 75 (1.1) |
| Other household member | 786 (11.1) |
| Nonrelated roommate | 367 (5.2) |
| Contact at workplace or school | 1,610 (22.7) |
| Nonhousehold relative | 177 (2.5) |
| Passenger on the same flight | 3,129 (44.1) |
| Friend | 523 (7.4) |
| Service person met at public place | 432 (6.1) |
| Contact phase | |
| Exposure to symptomatic index case-patient during symptomatic phase | 4,305 (60.6) |
| Exposure to symptomatic index case-patient the day before illness onset | 2,642 (37.2) |
| Exposure to person with subclinical index case | 149 (2.1) |
| Type of quarantine | |
| Quarantine station | 4,988 (70.3) |
| Home | 2,111 (29.7) |
*For index case-patients, median age (range) was 20 (1–75) y. For close contacts, median age (range) was 27 (0–99) y (data for 5,979 close contacts available). †Data for 7,032 close contacts available.