• Hyeri Seok, Seungkwan Lim, Ji-Yeon Kim, Chul Hee Park, Joon Ho Kim, Myoung Lyeol Woo, Hyejin Won, Yu Min Kang, Hong Sang Oh, Kyoung-Ho Song, Yun Jung Jung, Tark Kim, Soonam Jo, and Won Suk Choi.
• Division of Infectious Diseases, Department of Internal Medicine, Korea University Ansan Hospital, Korea University College of Medicine, Ansan, Korea.
• J. Korean Med. Sci. 2022 Apr 11; 37 (14): e106.

BackgroundAlthough several characteristics of coronavirus disease 2019 (COVID-19), an ongoing pandemic disease, have been identified, data on the infectivity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are limited.MethodsThis prospective cohort study was conducted to analyze the infectivity of SARS-CoV-2 based on data of all patients diagnosed with COVID-19 confirmed using real-time polymerase chain reaction test from January to April 2020 in Gyeonggi-do, the largest province in Korea.ResultsOf the 502 patients, 298 consisting of 106 clusters with 5,909 contacts were included. Of these, 277 (93.0%) were symptomatic, and the most common symptoms were cough, fever, sputum, sore throat, and headache. A total of 94 patients (31.5%) had pneumonia, while 8 (2.7%) died during the follow-up period. The secondary attack rate (SAR) in the study population was 3.5% (204/5,909). In exposure settings, the SAR was higher in religious gathering (13.5% [95% confidence interval, 10.7-16.8%]), workplaces (8.49% [95% CI, 6.08-11.74%]), and schools (6.38% [95% CI, 3.39-11.69%]) than in health care facilities (1.92% [95% CI, 1.45-2.55%]). Sore throat at any period, dyspnea at diagnosis or any period, lower cycle threshold value in the lower respiratory tract samples, leukocytosis, and higher bilirubin levels were associated with higher infectivity of COVID-19. The presence of symptoms was not related to the infectivity.ConclusionIn establishing the infection control strategies for COVID-19, the variables associated with high infectivity may be considered.© 2022 The Korean Academy of Medical Sciences.

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