Are 1 in 5 asymptomatic individuals with COVID-19 important superspreaders?

  • 22 Sep 2020

  • Liz Scherer
  • Clinical Essentials
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Takeaway

  • As many as 1 in 5 people who test positive for SARS-CoV-2 is asymptomatic but has nasopharynx viral loads comparable to patients with mild symptoms.
  • Mildly symptomatic and asymptomatic individuals demonstrate persistent positive upper respiratory reverse transcription (RT)-PCR findings at follow-up.

Why this matters

  • Although more data are needed, asymptomatic patients might be community superspreaders.
  • Patients who test positive for SARS-CoV-2 but present with no or mild symptoms may need to take extra preventative precautions, especially to minimize household transmission.

Key results

  • Of the 183 out of 213 patients included in the follow-up analyses, the median age (interquartile range) was 25.0 (21.5-34.0) for those who were asymptomatic and 26.5 (22.0-46.0) for those with symptoms.
  • Of the 183 who had follow-up RT-PCR data, 39 were asymptomatic and 144 had symptoms.
  • On follow-up:
    • 54% (n=21) of asymptomatic patients tested positive for virus gene sequences. 
    • 64% (n=92) of symptomatic patients tested positive (P=.25).
  • Mean cycle threshold (Ct) values for specific sequences between asymptomatic and symptomatic patients: 
    • gene: 31.15 vs 31.43 (P>.99).
    • RdRp gene: 32.26 vs 32.93 (P=.92).
    • gene: 33.05 vs 33.28 (P>.099).

Study design

  • Retrospective cohort analysis, Korea.
  • Funding: Korea Health Industry Development Institute.

Limitations

  • Young participants, single country; limited generalizability.
  • Recall bias.
  • Initial RT-PCR test results missing.
  • Time-related, follow-up testing bias.