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Despite initial resistance from some in the scientific community, it is now generally accepted that asymptomatic and presymptomatic COVID-19 cases can transmit the (SARS-2-CoV) pandemic virus. How often that occurs, however, is still a topic of debate.
But a new study, published this week in JAMA, challenges that assumption.The assumption has been that asymptomatic and presymptomatic cases likely shed far less virus than their symptomatic counterparts, and therefore pose less of a threat to the community.
In a study of 303 SARS-CoV-2 positive cases in South Korea (110 or 36.3% asymptomatic at time of isolation), they discovered that inferred viral loads (via cycle threshold (Ct) values from RT-PCR tests) were comparable among symptomatic and asymptomatic cases.
Furthermore, asymptomatic cases continued to test positive for the virus for nearly as long as symptomatic patients (avg 17 vs. 19 days).
While this doesn't exactly prove that asymptomatic carriers transmit the virus as readily as symptomatic cases, it weakens the argument against it. And since asymptomatic cases are more likely (than obviously ill individuals) to have contact with others, that probably increases their impact on community spread as well.
The full report can be read at the link below.
Original Investigation
August 6, 2020
Clinical Course and Molecular Viral Shedding Among Asymptomatic and Symptomatic Patients With SARS-CoV-2 Infection in a Community Treatment Center in the Republic of Korea
Seungjae Lee, MD1; Tark Kim, MD2; Eunjung Lee, MD1; et alCheolgu Lee, MD3; Hojung Kim, MD4; Heejeong Rhee, MD5; Se Yoon Park, MD1; Hyo-Ju Son, MD1; Shinae Yu, MD6; Jung Wan Park, MD6; Eun Ju Choo, MD2; Suyeon Park, MS7; Mark Loeb, MD8; Tae Hyong Kim, MD1
Author Affiliations Article Information
JAMA Intern Med. Published online August 6, 2020. doi:10.1001/jamainternmed.2020.3862
COVID-19 Resource Center
Key Points
Question
Are there viral load differences between asymptomatic and symptomatic patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection?
Findings
In this cohort study that included 303 patients with SARS-CoV-2 infection isolated in a community treatment center in the Republic of Korea, 110 (36.3%) were asymptomatic at the time of isolation and 21 of these (19.1%) developed symptoms during isolation. The cycle threshold values of reverse transcription–polymerase chain reaction for SARS-CoV-2 in asymptomatic patients were similar to those in symptomatic patients.
Meaning
Many individuals with SARS-CoV-2 infection remained asymptomatic for a prolonged period, and viral load was similar to that in symptomatic patients; therefore, isolation of infected persons should be performed regardless of symptoms.
