• Lei Luo, Dan Liu, Xinlong Liao, Xianbo Wu, Qinlong Jing, Jiazhen Zheng, Fanghua Liu, Shigui Yang, Hua Bi, Zhihao Li, Jianping Liu, Weiqi Song, Wei Zhu, Zhenghe Wang, Xiru Zhang, Qingmei Huang, Peiliang Chen, Huamin Liu, Xin Cheng, Miaochun Cai, Pei Yang, Xingfen Yang, Zhigang Han, Jinling Tang, Yu Ma, and Chen Mao.
• Guangzhou Center for Disease Control and Prevention, Guangzhou, China (L.L., X.L., Q.J., F.L., H.B., J.L., W.Z., Z.H., Y.M.).
• Ann. Intern. Med. 2020 Dec 1; 173 (11): 879887879-887.

BackgroundRisk for transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to close contacts of infected persons has not been well estimated.ObjectiveTo evaluate the risk for transmission of SARS-CoV-2 to close contacts in different settings.DesignProspective cohort study.SettingClose contacts of persons infected with SARS-CoV-2 in Guangzhou, China.Participants3410 close contacts of 391 index cases were traced between 13 January and 6 March 2020. Data on the setting of the exposure, reverse transcriptase polymerase chain reaction testing, and clinical characteristics of index and secondary cases were collected.MeasurementCoronavirus disease 2019 (COVID-19) cases were confirmed by guidelines issued by China. Secondary attack rates in different settings were calculated.ResultsAmong 3410 close contacts, 127 (3.7% [95% CI, 3.1% to 4.4%]) were secondarily infected. Of these 127 persons, 8 (6.3% [CI, 2.1% to 10.5%]) were asymptomatic. Of the 119 symptomatic cases, 20 (16.8%) were defined as mild, 87 (73.1%) as moderate, and 12 (10.1%) as severe or critical. Compared with the household setting (10.3%), the secondary attack rate was lower for exposures in health care settings (1.0%; odds ratio [OR], 0.09 [CI, 0.04 to 0.20]) and on public transportation (0.1%; OR, 0.01 [CI, 0.00 to 0.08]). The secondary attack rate increased with the severity of index cases, from 0.3% (CI, 0.0% to 1.0%) for asymptomatic to 3.3% (CI, 1.8% to 4.8%) for mild, 5.6% (CI, 4.4% to 6.8%) for moderate, and 6.2% (CI, 3.2% to 9.1%) for severe or critical cases. Index cases with expectoration were associated with higher risk for secondary infection (13.6% vs. 3.0% for index cases without expectoration; OR, 4.81 [CI, 3.35 to 6.93]).LimitationThere was potential recall bias regarding symptom onset among patients with COVID-19, and the symptoms and severity of index cases were not assessed at the time of exposure to contacts.ConclusionHousehold contact was the main setting for transmission of SARS-CoV-2, and the risk for transmission of SARS-CoV-2 among close contacts increased with the severity of index cases.Primary Funding SourceGuangdong Province Higher Vocational Colleges and Schools Pearl River Scholar Funded Scheme.

25 keywords...

hide…