J Korean Med Sci.  2020 Aug;35(32):e297. 10.3346/jkms.2020.35.e297.

Clinical Characteristics of COVID-19: Clinical Dynamics of Mild Severe Acute Respiratory Syndrome Coronavirus 2 Infection Detected by Early Active Surveillance

  • 1Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea
  • 2Department of Internal Medicine, Seoul Metropolitan Government-Seoul National University Boramae Medical Center, Seoul, Korea
  • 3Department of Internal Medicine, Gyeonggi Provincial Medical Center Paju Hospital, Paju, Korea
  • 4Department of Internal Medicine, Jeonbuk National University Medical School, Jeonju, Korea
  • 5Department of Internal Medicine, Gyeonggi Provincial Medical Center Suwon Hospital, Suwon, Korea
  • 6Department of Internal Medicine, Kangwon National University School of Medicine, Chuncheon, Korea
  • 7Department of Internal Medicine, Chung-Ang University Hospital, Seoul, Korea
  • 8Department of Internal Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea
  • 9Department of Internal Medicine, Gangwon-do Wonju Medical Center, Wonju, Korea
  • 10Department of Internal Medicine, Kyung Hee University Hospital, Seoul, Korea
  • 11Department of Internal Medicine, Inje University Busan Paik Hospital, Busan, Korea
  • 12Department of Internal Medicine, Inje University Sanggye Paik Hospital, Seoul, Korea


There is limited information describing the presenting characteristics and dynamic clinical changes in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection diagnosed in the early phase of illness. This study is a case series of patients with coronavirus disease 2019 (COVID-19) admitted to 11 hospitals in Korea.
Patients with confirmed SARS-CoV-2 infection by positive polymerase chain reaction (PCR) testing of respiratory specimens by active surveillance that were finally discharged between February 20 and April 30, 2020 were included. Patients were classified into mild and non-mild groups on initial admission according to oxygen demand and Sequential Organ Failure Assessment score, and the mild group was followed up and subgrouped into non-aggravation and aggravation groups.
A total of 161 patients with SARS-CoV2 infection were enrolled. Among the mild group of 136 patients, 11.7% of patients experienced clinical aggravation during hospitalization, but there was no initial clinical parameter on admission predicting their aggravation. Fever (odds ratio [OR], 4.56), thrombocytopenia (OR, 12.87), fever (OR, 27.22) and lactate dehydrogenase (LDH) > 300 U/L (OR, 18.35), and CRP > 1 mg/dL (OR, 11.31) significantly indicated aggravation in the 1st, 2nd, 3rd, and 4th 5-day periods, respectively. PCR positivity lasted for a median of 22 days and 32 days after the onset of illness in the nonaggravation and aggravation groups, respectively.
Old age was associated with early severe presentation. Clinical aggravation among asymptomatic or mild patients could not be predicted initially but was heralded by fever and several laboratory markers during the clinical course.


COVID-19; SARS-CoV-2; Korea; Mild; Active Surveillance
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