Asymptomatic SARS-CoV-2: Microbial Minutes

Nov. 10, 2020

What do we know about asymptomatic transmission of SARS-CoV-2 in children and adults, and how does the immune system respond to asymptomatic SARS-CoV-2 infection?

What's Hot in the Microbial Sciences?

ASM presents Microbial Minutes, a monthly video series of trending topics in the microbial sciences.

The potential for SARS-CoV-2 to be spread by people who never exhibit symptoms of disease, or those who exhibit delayed symptom onset, is a serious concern and possible contributing factor to the pandemic spread of this virus. Not surprisingly, “stealth transmission” is especially difficult to identify and contain. Here we dive into the research that seeks to explain how this virus behaves, as it pertains to asymptomatic cases. The papers and key take-away points discussed in this Microbial Minutes are listed below.

How common is asymptomatic SARS-CoV-2 infection? 

He J. et al. Proportion of asymptomatic coronavirus disease 2019: A systemic review and meta-analysis. Journal of Medical Virology. July 21, 2020.

Oran D.P. et al. Prevalence of Asymptomatic SARS-CoV-2 Infection. A Narrative Review. American College of Physicians Public Health Emergency Collection. June 3, 2020.

Are patients with asymptomatic SARS-CoV-2 contagious?

Lee S. et al. Clinical Course and Molecular Viral Shedding Among Asymptomatic and Symptomatic Patients With SARS-CoV-2 Infection in a Community Treatment Center in Republic of Korea. JAMA Internal Medicine. Aug. 6, 2020.
Zou L. et al. SARS-CoV-2 Viral Load in Upper Respiratory Specimens of Infected Patients. New England Journal of Medicine. March 19, 2020.

Arons M.M. et al. Presymptomatic SARS-CoV-2 Infecitons and Transmission in a Skilled Nursing Facility. New England Journal of Medicine. May 28, 2020.

Hu Z. et al. Clinical characteristics of 24 asymptomatic infections with COVID-19 screened aong close contacts in Nanjing, China. Sci China Life Sci. May 2020.

Kociolek L.K et al. Comparison of upper respiratory viral load distributions in asymptomatic and symptomatic children diagnosed with SARS-CoV-2 infection in pediatric hospital testing programs. Journal of Clinical Microbiology. Oct. 22, 2020.

Can other respiratory viruses be asymptomatic? 

Toner E. Do Publi Health and Infection Control Measures Work to Prevent the Spread of Flu? Clinician's Biosafety News, Johns Hopkins Center for Health Security. Oct. 31, 2005.

How does the immune system respond to asymptomatic infection? 

Lei Q et al. Antibody dynamics to SARS-CoV-2 in asymptomatic COVID-19 infections. European Journal of Allergy and Clinical Immunology. Oct. 10, 2020.

Shirin T. et al. Antibody responses after COVID-19 infection in patients who are mildly symptomatic or asymptomatic in Bangladesh. International Journal of Infectious Diseases. Oct. 5, 2020.

Take-Away Points

  • Asymptomatic patients are still contagious.
  • Asymptomatic patients test negative approximately 2 days before symptomatic patients.
  • Asymptomatic children are potentially less contagious than asymptomatic adults.

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Author: Ashley Hagen, M.S.

Ashley Hagen, M.S.
Ashley Hagen, M.S. is the Scientific and Digital Editor for the American Society for Microbiology and host of ASM's Microbial Minutes.