Table 1. Demographic Characteristics of Index Patients and Close Contacts.
| Characteristics | No. (%) | |
|---|---|---|
| Index patients (n = 730) | Close contacts (n = 8852)a | |
| Age, median (IQR), y | 46 (36-56) | 41 (28-54) |
| Age group, y | ||
| <20 | 22 (3.0) | 1101 (12.4) |
| 20-29 | 67 (9.2) | 1337 (15.1) |
| 30-39 | 153 (21.0) | 1800 (20.3) |
| 40-49 | 174 (23.8) | 1718 (19.4) |
| 50-59 | 176 (24.1) | 1445 (16.3) |
| 60-69 | 90 (12.3) | 851 (9.6) |
| ≥70 | 48 (6.6) | 600 (6.8) |
| Sex | ||
| Female | 356 (48.8) | 4173 (47.1) |
| Male | 374 (51.2) | 4679 (52.9) |
| Severity of COVID-19 in index patient | ||
| Asymptomatic | 81 (11.1) | 1098 (12.2) |
| Mild | 336 (46.0) | 4867 (54.1) |
| Moderate | 313 (42.9) | 3034 (33.7) |
| Primary contact type | ||
| Conversation | NA | 2687 (29.9) |
| Dine together | NA | 1066 (11.8) |
| Enclosed space without direct contact | NA | 1408 (15.6) |
| Health care setting | NA | 459 (5.1) |
| Live together | NA | 1499 (16.7) |
| Multiple | NA | 44 (0.5) |
| Shared transportation | NA | 1055 (11.7) |
| Others | NA | 781 (8.7) |
| Source of index patient | ||
| Importationb | 42 (5.8) | 439 (4.9) |
| Local | 688 (94.2) | 8560 (95.1) |
Abbreviation: NA, not applicable.
For contact characteristics, the statistics in this column are assigned to contacts. For index case characteristics (ie, severity of COVID-19 in index patient, primary contact type, source of index patient), the statistics in this column represent the number of contacts exposed to that type of index patient. For example, 1098 contacts were exposed to an asymptomatic index patient. Also, 8560 contacts were exposed to a local index patient. For these characteristics there were 8999 contact events among 8852 total contacts, as some contacts were exposed to multiple index patients. Therefore, for index patient characteristics (eg, severity of COVID-19 in index patient) assigned to contacts there is a sum of 8999 rather than 8852, which is the sum for contact characteristics in this column (eg, sex).
Not infected in Zhejiang Province.