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. 2020 Apr 27;20(8):911–919. doi: 10.1016/S1473-3099(20)30287-5

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Time between symptom onset and SARS-CoV-2 confirmation (A), admission to hospital (B), and isolation among cases (C) detected by contact-based and symptom-based surveillance

The maximum-likelihood estimates for the parametric distribution of the cumulative distribution function are shown, along with 1000 parametric bootstrap estimates of the cumulative distribution function. Panel A shows estimates of the proportion of cases who are confirmed by RT-PCR, according to the number of days after symptom onset. We estimated that 50% of cases detected through symptom-based surveillance were confirmed by RT-PCR within 4·6 days (95% CI 4·2–5·0) after symptom onset, and 95% were confirmed by RT-PCR within 12·7 days (11·5–13·8) after symptom onset. Contact-based surveillance reduced the days from symptom onset to RT-PCR confirmation to 2·9 days (95% CI 2·4–3·4) in 50% of cases and to 6·6 days (5·3–8·0) in 95% of cases. Panel B shows estimates of the proportion of cases who were admitted to hospital, according to the number of days after symptom onset. We estimated that 50% of the cases detected through symptom-based surveillance were admitted to hospital by 3·4 days (95% CI 3·1–3·8) after symptom onset, and 95% by 12·4 days (10·9–13·8). Contact-based surveillance reduced the days from symptom onset to hospital admission to 2·1 days (95% CI 1·7–2·6) in 50% of cases, and 6·0 days (95% CI 4·5–7·5) in 95% of cases. Panel C shows estimates of the proportion of cases isolated, according to number of days after symptom onset. We estimated that 50% of cases detected through symptom-based surveillance were isolated by 3·4 days (95% CI 3·1–3·7) after symptom onset, and 95% by 12·2 days (95% CI 10·8–13·6). Contact-based surveillance reduced the days from symptom onset to isolation to 2·2 days (95% CI 1·7–2·6) in 50% of cases, and to 6·5 days (4·7–8·2) in 95% of cases.