Patterns of viral clearance in the natural course of asymptomatic COVID-19: Comparison with symptomatic non-severe COVID-19

Int J Infect Dis. 2020 Oct:99:279-285. doi: 10.1016/j.ijid.2020.07.070. Epub 2020 Aug 5.


Objectives: The aim of this study was to elucidate patterns of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) clearance in the natural course of asymptomatic coronavirus disease 2019 (COVID-19).

Methods: Consecutive patients with non-severe COVID-19 were included retrospectively. Asymptomatic patients with a normal body temperature and no evidence of pneumonia throughout the disease course were assigned to the asymptomatic group. The reverse transcription PCR (RT-PCR) assay was repeated every two to five days after the first follow-up RT-PCR assay. Negative conversion was defined as two consecutive negative RT-PCR assay results within a 24-h interval. Rebound of the cycle threshold (Ct) value was defined as negative from the single RT-PCR assay and positive from the following assay.

Results: Among a total of 396 patients identified (median age 42.5 years (interquartile range (IQR) 25.0-55.0 years), 35.6% male), 68 (17.2%) were assigned to the asymptomatic group and 328 (82.8%) to the symptomatic group. The time until negative conversion was significantly shorter in the asymptomatic group than in the symptomatic group: median 14.5 days (IQR 11.0-21.0 days) and 18.0 days (IQR 15.0-22.0 days), respectively (p = 0.001). Rebound of Ct values was observed in 78 patients (19.7%).

Conclusions: Time until negative conversion is shorter in asymptomatic COVID-19 than in symptomatic COVID-19. Rebound of Ct values is not uncommon.

Keywords: Asymptomatic; COVID-19; Coronavirus disease 2019; Negative conversion; SARS-CoV-2; Viral clearance.

Publication types

  • Comparative Study

MeSH terms

  • Adult
  • Asymptomatic Diseases
  • Betacoronavirus / genetics*
  • COVID-19
  • Cohort Studies
  • Coronavirus Infections / diagnosis
  • Coronavirus Infections / epidemiology*
  • Coronavirus Infections / virology
  • Disease Progression
  • Female
  • Humans
  • Male
  • Middle Aged
  • Pandemics*
  • Pneumonia, Viral / diagnosis
  • Pneumonia, Viral / epidemiology*
  • Pneumonia, Viral / virology
  • Republic of Korea / epidemiology
  • Retrospective Studies
  • Reverse Transcriptase Polymerase Chain Reaction
  • SARS-CoV-2
  • Viral Load