Volume 26, Number 8—August 2020
Research Letter
Secondary Transmission of Coronavirus Disease from Presymptomatic Persons, China
Table
Characteristics of and secondary attack rates among 369 close contacts of persons with presymptomatic coronavirus disease 2019, China*
| Variable |
No. contacts |
No. infected |
Attack rate, % (95% CI) |
Relative risk (95% CI) |
| Sex | ||||
| M | 217 | 5 | 2.3 (0.1–5.2) | Referent |
| F |
152 |
7 |
4.6 (2.2–8.9) |
2.1 (0.6–6.6) |
| Age | ||||
| ≤17 | 46 | 2 | 4.3 (1.2–14.5) | Referent |
| 18–30 | 104 | 3 | 2.9 (1.0–8.1) | 0.7 (0.1–4.1) |
| 31–40 | 72 | 1 | 1.4 (0.2–7.4) | 0.4 (0.03–3.5) |
| 41–50 | 68 | 1 | 1.5 (0.3–7.9) | 0.4 (0.03–3.7) |
| 51–60 | 54 | 3 | 5.6 (1.9–15.1) | 1.3 (0.2–8.1) |
| ≥61 |
25 |
2 |
8.0 (1.4–27.5) |
1.9 (0.3–14.5) |
| Index case-patient status* | ||||
| Asymptomatic | 119 | 1 | 0.8 (0.2–5.6) | Referent |
| Mild symptoms | 141 | 5 | 3.5 (1.5–8.0) | 4.3 (0.5–37.7) |
| Moderate symptoms | 87 | 5 | 5.7 (2.5–12.8) | 7.2 (0.8–62.7) |
| Severe symptoms |
22 |
1 |
4.5 (0.8–21.8) |
5.6 (0.3–93.4) |
| Contact mode | ||||
| Social interaction with friends or relatives | 66 | 1 | 1.5 (0.3–8.1) | Referent |
| Lived together | 62 | 10 | 16.1 (9.0–27.2) | 12.5 (1.6–100.8) |
| Worked together | 119 | 0 | 0 | 0 |
| Social interaction with strangers |
122 |
1 |
0.8 (0.2–4.9) |
0.5 (0.03–8.7) |
| Contact frequency† | ||||
| Rare | 149 | 1 | 0.7 (0.1–3.7) | Referent |
| Moderate | 159 | 1 | 0.6 (0.1–3.5) | 0.9 (0.1–15.1) |
| Frequent |
61 |
10 |
16.4 (9.2–27.6) |
29.0 (3.6–232.3) |
| *Status as of March 30, 2020, based on the person’s clinical course assessed by a physician. Moderate symptoms included fever, respiratory symptoms, and radiographic evidence of pneumonia. Severe symptoms included breathing rate >30/min; oxygen saturation level <93% at rest; oxygen concentration level PaO2/FiO2 <300 mmHg (1 mmHg = 0.133kPa); lung infiltrates >50% within the past 24–48 h; respiratory failure requiring mechanical ventilation; septic shock; or multiple organ dysfunction or failure. All other symptomatic cases were classified as mild.
†Rare contact was defined as contacted with index cases <2 times during 2 days preceding confirmation of infection. Moderate contact was defined as contacted with index cases 3–5 times during 2 days preceding confirmation of infection. Frequent contact was defined as contacted with index cases >5 times during 2 days preceding confirmation of infection. |
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1These first authors contributed equally to this article.
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Page updated: July 19, 2020
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