Epidemiology and Transmission of COVID-19 in Shenzhen China: Analysis of 391 cases and 1,286 of their close contacts

Qifang Bi; Yongsheng Wu; Shujiang Mei; Chenfei Ye; Xuan Zou; Zhen Zhang; Xiaojian Liu; Lan Wei; Shaun A Truelove; Tong Zhang; Wei Gao; Cong Cheng; Xiujuan Tang; Xiaoliang Wu; Yu Wu; Binbin Sun; Suli Huang; Yu Sun; Juncen Zhang; Ting Ma; Justin Lessler; Teijian Feng

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 PCR confirmed, according to the number of days after symptom onset. We estimated that 50% of the cases detected through symptom-based surveillance were PCR confirmed by 4.6 days (95% CI, 4.2 to 5.0) after symptom onset, in 95% by 12.7 days (95% CI, 11.5 to 13.8) after symptom onset. Contact-based surveillance reduced the days from symptom onset to PCR confirmation to 2.9 days (95% CI, 2.4, 3.4) in 50% cases and 6.6 days (95%CI, 5.3, 8.0) in 95% cases. Panel B shows estimates of the proportion of cases who are hospitalized, according to the number of days after symptom onset. We estimated that 50% of the cases detected through symptom-based surveillance were hospitalized by 3.4 days (95% CI, 3.1 to 3.8) after symptom onset, in 95% by 12.4 days (95% CI, 10.9 to 13.8). Contact-based surveillance reduced the days from symptom onset to hospitalization to 2.1 days (95% CI, 1.7, 2.6) in 50% cases, and 6.0 days (95% CI, 4.5, 7.5) in 95% cases. Panel C shows estimates of the proportion of cases isolated, according to the number of days after symptom onset. We estimated that 50% of the cases detected through symptom-based surveillance were isolated by 3.4 days (95% CI, 3.1 to 3.7) after symptom onset, in 95% by 12.2 days (95% CI, 10.8 to 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% cases, and 6.5 days (95% CI, 4.7, 8.2) in 95% cases.