The Shenzhen CDC identified 391 SARS-CoV-2 cases from January 14 to February 12, 2020 and 1286 close contacts. We compare cases identified through symptomatic surveillance and contact tracing, and estimate the time from symptom onset to confirmation, isolation, and hospitalization. We estimate metrics of disease transmission and analyze factors influencing transmission risk.
Cases were older than the general population (mean age 45) and balanced between males (187) and females (204). Ninety-one percent had mild or moderate clinical severity at initial assessment. Three have died, 225 have recovered (median time to recovery is 21 days). Cases were isolated on average 4.6 days after developing symptoms; contact tracing reduced this by 1.9 days. Household contacts and those travelling with a case where at higher risk of infection (ORs 6 and 7) than other close contacts. The household secondary attack rate was 15%, and children were as likely to be infected as adults. The observed reproductive number was 0.4, with a mean serial interval of 6.3 days.
Total 9% Severe 35/391
@article{bi_epidemiology_2020, title = {Epidemiology and {Transmission} of {COVID}-19 in {Shenzhen} {China}: {Analysis} of 391 cases and 1,286 of their close contacts}, copyright = {© 2020, Posted by Cold Spring Harbor Laboratory. This pre-print is available under a Creative Commons License (Attribution-NoDerivs 4.0 International), CC BY-ND 4.0, as described at http://creativecommons.org/licenses/by-nd/4.0/}, issn = {10.1101/2020.03.03.20028423}, shorttitle = {Epidemiology and {Transmission} of {COVID}-19 in {Shenzhen} {China}}, url = {https://www.medrxiv.org/content/10.1101/2020.03.03.20028423v2}, doi = {10.1101/2020.03.03.20028423}, abstract = {{\textless}p{\textgreater}Background Rapid spread of SARS-CoV-2 in Wuhan prompted heightened surveillance in Shenzhen and elsewhere in China. The resulting data provide a rare opportunity to measure key metrics of disease course, transmission, and the impact of control. Methods The Shenzhen CDC identified 391 SARS-CoV-2 cases from January 14 to February 12, 2020 and 1286 close contacts. We compare cases identified through symptomatic surveillance and contact tracing, and estimate the time from symptom onset to confirmation, isolation, and hospitalization. We estimate metrics of disease transmission and analyze factors influencing transmission risk. Findings Cases were older than the general population (mean age 45) and balanced between males (187) and females (204). Ninety-one percent had mild or moderate clinical severity at initial assessment. Three have died, 225 have recovered (median time to recovery is 21 days). Cases were isolated on average 4.6 days after developing symptoms; contact tracing reduced this by 1.9 days. Household contacts and those travelling with a case where at higher risk of infection (ORs 6 and 7) than other close contacts. The household secondary attack rate was 15%, and children were as likely to be infected as adults. The observed reproductive number was 0.4, with a mean serial interval of 6.3 days. Interpretation Our data on cases as well as their infected and uninfected close contacts provide key insights into SARS-CoV-2 epidemiology. This work shows that heightened surveillance and isolation, particularly contact tracing, reduces the time cases are infectious in the community, thereby reducing R. Its overall impact, however, is uncertain and highly dependent on the number of asymptomatic cases. We further show that children are at similar risk of infection as the general population, though less likely to have severe symptoms; hence should be considered in analyses of transmission and control.{\textless}/p{\textgreater}}, language = {en}, urldate = {2020-03-25}, journal = {medRxiv}, author = {Bi, Qifang and Wu, Yongsheng and Mei, Shujiang and Ye, Chenfei and Zou, Xuan and Zhang, Zhen and Liu, Xiaojian and Wei, Lan and Truelove, Shaun A. and Zhang, Tong and Gao, Wei and Cheng, Cong and Tang, Xiujuan and Wu, Xiaoliang and Wu, Yu and Sun, Binbin and Huang, Suli and Sun, Yu and Zhang, Juncen and Ma, Ting and Lessler, Justin and Feng, Teijian}, month = mar, year = {2020}, pages = {2020.03.03.20028423}, file = {Full Text PDF:/Users/michael/Zotero/storage/Y8FFCTQR/Bi et al. - 2020 - Epidemiology and Transmission of COVID-19 in Shenz.pdf:application/pdf;Snapshot:/Users/michael/Zotero/storage/2BR6JX9I/2020.03.03.html:text/html} }