Presymptomatic and Asymptomatic Transmission of COVID-19

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Reports released by CDC in March and April characterize asymptomatic and presymptomatic spread of COVID-19 in China, in clusters of cases in Singapore, on the Diamond Princess cruise ship, and in a Seattle nursing home. In these studies, “asymptomatic” describes individuals who did not exhibit symptoms when tested for infection, and “presymptomatic” designates those previously categorized as asymptomatic who later developed symptoms. Information from these reports appears below.

From “Presymptomatic Transmission of SARS-CoV-2 — Singapore, January 23–March 16, 2020”:

“Presymptomatic transmission might occur through generation of respiratory droplets or possibly through indirect transmission. Speech and other vocal activities such as singing have been shown to generate air particles, with the rate of emission corresponding to voice loudness. News outlets have reported that during a choir practice in Washington on March 10, presymptomatic transmission likely played a role in SARS-CoV-2 transmission to approximately 40 of 60 choir members.”

SOURCES

CDC: Morbidity and Mortality Weekly Report, “
Asymptomatic and Presymptomatic SARS-CoV-2 Infections in Residents of a Long-Term Care Skilled Nursing Facility — King County, Washington, March 2020
” (April 2020).

CDC:
Morbidity and Mortality Weekly Report
, “
Presymptomatic Transmission of SARS-CoV-2 — Singapore, January 23–March 16, 2020
”
(April 2020). CDC:
Morbidity and Mortality Weekly Report
, “
Public Health Responses to COVID-19 Outbreaks on Cruise Ships — Worldwide, February–March 2020
” (March 2020).

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In August, The Knoxville News Sentinel reported that a student intern and a researcher at Oak Ridge Associated Universities had devised an experiment to replicate the McCluskey incident in order to study the effects of radiation on the body. By irradiating vials of their own blood for different lengths of time, the researchers hope to generate data that clinicians and first responders can refer to following an exposure incident.