What is known about asymptomatic and presymptomatic transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)?

Updated: Jun 16, 2020
  • Author: Medscape Drugs & Diseases; more...
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Epidemiologic studies have documented severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission during the presymptomatic incubation period, and asymptomatic transmission has been suggested in other reports. [1]

Virologic studies using reverse transcription polymerase chain reaction (RT-PCR) have also detected SARS-CoV-2 with low cycle thresholds, indicating larger quantities of viral RNA. Viable virus has also been cultured among persons with asymptomatic and presymptomatic SARS-CoV-2 infection. [1]

It is not yet known what exact degree of SARS-CoV-2 viral RNA shedding confers risk of transmission, but the greatest transmission risk is thought to be when patients are symptomatic, because viral shedding is greatest at the time of symptom onset and falls over the course of several days to weeks. [1]  However, the proportion of SARS-CoV-2 transmission in the population due to asymptomatic or presymptomatic infection compared to symptomatic infection is unclear.

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