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Epidemiology and transmission of COVID-19 in 391 cases and 1286 of their close contacts in Shenzhen, China: a retrospective cohort study.
Lancet Infect Dis. 2020 08; 20(8):911-919.LI

Abstract

BACKGROUND

Rapid spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Wuhan, China, prompted heightened surveillance in Shenzhen, China. The resulting data provide a rare opportunity to measure key metrics of disease course, transmission, and the impact of control measures.

METHODS

From Jan 14 to Feb 12, 2020, the Shenzhen Center for Disease Control and Prevention identified 391 SARS-CoV-2 cases and 1286 close contacts. We compared cases identified through symptomatic surveillance and contact tracing, and estimated the time from symptom onset to confirmation, isolation, and admission to hospital. We estimated metrics of disease transmission and analysed factors influencing transmission risk.

FINDINGS

Cases were older than the general population (mean age 45 years) and balanced between males (n=187) and females (n=204). 356 (91%) of 391 cases had mild or moderate clinical severity at initial assessment. As of Feb 22, 2020, three cases had died and 225 had recovered (median time to recovery 21 days; 95% CI 20-22). Cases were isolated on average 4·6 days (95% CI 4·1-5·0) after developing symptoms; contact tracing reduced this by 1·9 days (95% CI 1·1-2·7). Household contacts and those travelling with a case were at higher risk of infection (odds ratio 6·27 [95% CI 1·49-26·33] for household contacts and 7·06 [1·43-34·91] for those travelling with a case) than other close contacts. The household secondary attack rate was 11·2% (95% CI 9·1-13·8), and children were as likely to be infected as adults (infection rate 7·4% in children <10 years vs population average of 6·6%). The observed reproductive number (R) was 0·4 (95% CI 0·3-0·5), with a mean serial interval of 6·3 days (95% CI 5·2-7·6).

INTERPRETATION

Our data on cases as well as their infected and uninfected close contacts provide key insights into the epidemiology of SARS-CoV-2. This analysis shows that isolation and contact tracing reduce the time during which cases are infectious in the community, thereby reducing the R. The overall impact of isolation and contact tracing, however, is uncertain and highly dependent on the number of asymptomatic cases. Moreover, children are at a similar risk of infection to the general population, although less likely to have severe symptoms; hence they should be considered in analyses of transmission and control.

FUNDING

Emergency Response Program of Harbin Institute of Technology, Emergency Response Program of Peng Cheng Laboratory, US Centers for Disease Control and Prevention.

Authors+Show Affiliations

Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.Department of Public Health Information, Shenzhen, China.Department of Communicable Diseases Control and Prevention, Shenzhen, China.School of Electronic and Information Engineering, Harbin Institute of Technology at Shenzhen, Shenzhen, China; Artificial Intelligence Research Center, Peng Cheng Laboratory, Shenzhen, China.Shenzhen Center for Disease Control and Prevention, Shenzhen, China.Department of Public Health Information, Shenzhen, China.Department of Public Health Information, Shenzhen, China.Department of Public Health Information, Shenzhen, China.Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.Artificial Intelligence Research Center, Peng Cheng Laboratory, Shenzhen, China.Department of Communicable Diseases Control and Prevention, Shenzhen, China.Department of Communicable Diseases Control and Prevention, Shenzhen, China.Department of Communicable Diseases Control and Prevention, Shenzhen, China.Department of Communicable Diseases Control and Prevention, Shenzhen, China.Department of School Health, Shenzhen, China.School of Computer Science, Harbin Institute of Technology at Shenzhen, Shenzhen, China; Artificial Intelligence Research Center, Peng Cheng Laboratory, Shenzhen, China.Department of Environment and Health, Shenzhen, China.Artificial Intelligence Research Center, Peng Cheng Laboratory, Shenzhen, China.Artificial Intelligence Research Center, Peng Cheng Laboratory, Shenzhen, China.School of Electronic and Information Engineering, Harbin Institute of Technology at Shenzhen, Shenzhen, China; Artificial Intelligence Research Center, Peng Cheng Laboratory, Shenzhen, China. Electronic address: tma@hit.edu.cn.Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA. Electronic address: justin@jhu.edu.Shenzhen Center for Disease Control and Prevention, Shenzhen, China. Electronic address: fengtiej@126.com.

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

32353347

Citation

Bi, Qifang, et al. "Epidemiology and Transmission of COVID-19 in 391 Cases and 1286 of Their Close Contacts in Shenzhen, China: a Retrospective Cohort Study." The Lancet. Infectious Diseases, vol. 20, no. 8, 2020, pp. 911-919.
Bi Q, Wu Y, Mei S, et al. Epidemiology and transmission of COVID-19 in 391 cases and 1286 of their close contacts in Shenzhen, China: a retrospective cohort study. Lancet Infect Dis. 2020;20(8):911-919.
Bi, Q., Wu, Y., Mei, S., Ye, C., Zou, X., Zhang, Z., Liu, X., Wei, L., Truelove, S. A., Zhang, T., Gao, W., Cheng, C., Tang, X., Wu, X., Wu, Y., Sun, B., Huang, S., Sun, Y., Zhang, J., ... Feng, T. (2020). Epidemiology and transmission of COVID-19 in 391 cases and 1286 of their close contacts in Shenzhen, China: a retrospective cohort study. The Lancet. Infectious Diseases, 20(8), 911-919. https://doi.org/10.1016/S1473-3099(20)30287-5
Bi Q, et al. Epidemiology and Transmission of COVID-19 in 391 Cases and 1286 of Their Close Contacts in Shenzhen, China: a Retrospective Cohort Study. Lancet Infect Dis. 2020;20(8):911-919. PubMed PMID: 32353347.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Epidemiology and transmission of COVID-19 in 391 cases and 1286 of their close contacts in Shenzhen, China: a retrospective cohort study. AU - Bi,Qifang, AU - Wu,Yongsheng, AU - Mei,Shujiang, AU - Ye,Chenfei, AU - Zou,Xuan, AU - Zhang,Zhen, AU - Liu,Xiaojian, AU - Wei,Lan, AU - Truelove,Shaun A, AU - Zhang,Tong, AU - Gao,Wei, AU - Cheng,Cong, AU - Tang,Xiujuan, AU - Wu,Xiaoliang, AU - Wu,Yu, AU - Sun,Binbin, AU - Huang,Suli, AU - Sun,Yu, AU - Zhang,Juncen, AU - Ma,Ting, AU - Lessler,Justin, AU - Feng,Tiejian, Y1 - 2020/04/27/ PY - 2020/03/02/received PY - 2020/03/31/revised PY - 2020/04/02/accepted PY - 2020/5/1/pubmed PY - 2020/8/12/medline PY - 2020/5/1/entrez SP - 911 EP - 919 JF - The Lancet. Infectious diseases JO - Lancet Infect Dis VL - 20 IS - 8 N2 - BACKGROUND: Rapid spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Wuhan, China, prompted heightened surveillance in Shenzhen, China. The resulting data provide a rare opportunity to measure key metrics of disease course, transmission, and the impact of control measures. METHODS: From Jan 14 to Feb 12, 2020, the Shenzhen Center for Disease Control and Prevention identified 391 SARS-CoV-2 cases and 1286 close contacts. We compared cases identified through symptomatic surveillance and contact tracing, and estimated the time from symptom onset to confirmation, isolation, and admission to hospital. We estimated metrics of disease transmission and analysed factors influencing transmission risk. FINDINGS: Cases were older than the general population (mean age 45 years) and balanced between males (n=187) and females (n=204). 356 (91%) of 391 cases had mild or moderate clinical severity at initial assessment. As of Feb 22, 2020, three cases had died and 225 had recovered (median time to recovery 21 days; 95% CI 20-22). Cases were isolated on average 4·6 days (95% CI 4·1-5·0) after developing symptoms; contact tracing reduced this by 1·9 days (95% CI 1·1-2·7). Household contacts and those travelling with a case were at higher risk of infection (odds ratio 6·27 [95% CI 1·49-26·33] for household contacts and 7·06 [1·43-34·91] for those travelling with a case) than other close contacts. The household secondary attack rate was 11·2% (95% CI 9·1-13·8), and children were as likely to be infected as adults (infection rate 7·4% in children <10 years vs population average of 6·6%). The observed reproductive number (R) was 0·4 (95% CI 0·3-0·5), with a mean serial interval of 6·3 days (95% CI 5·2-7·6). INTERPRETATION: Our data on cases as well as their infected and uninfected close contacts provide key insights into the epidemiology of SARS-CoV-2. This analysis shows that isolation and contact tracing reduce the time during which cases are infectious in the community, thereby reducing the R. The overall impact of isolation and contact tracing, however, is uncertain and highly dependent on the number of asymptomatic cases. Moreover, children are at a similar risk of infection to the general population, although less likely to have severe symptoms; hence they should be considered in analyses of transmission and control. FUNDING: Emergency Response Program of Harbin Institute of Technology, Emergency Response Program of Peng Cheng Laboratory, US Centers for Disease Control and Prevention. SN - 1474-4457 UR - https://www.unboundmedicine.com/medline/citation/32353347/Epidemiology_and_transmission_of_COVID_19_in_391_cases_and_1286_of_their_close_contacts_in_Shenzhen_China:_a_retrospective_cohort_study_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S1473-3099(20)30287-5 DB - PRIME DP - Unbound Medicine ER -