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Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread rapidly throughout
the world since the first cases of coronavirus disease 2019 (COVID-19) were observed
in December 2019 in Wuhan, China. It has been suspected that infected persons who
remain asymptomatic play a significant role in the ongoing pandemic, but their relative
number and effect have been uncertain. The authors sought to review and synthesize
the available evidence on asymptomatic SARS-CoV-2 infection. Asymptomatic persons
seem to account for approximately 40% to 45% of SARS-CoV-2 infections, and they can
transmit the virus to others for an extended period, perhaps longer than 14 days.
Asymptomatic infection may be associated with subclinical lung abnormalities, as detected
by computed tomography. Because of the high risk for silent spread by asymptomatic
persons, it is imperative that testing programs include those without symptoms. To
supplement conventional diagnostic testing,
which is constrained by capacity, cost, and its one-off nature, innovative tactics
for public health surveillance, such as crowdsourcing digital wearable data and monitoring
sewage sludge, might be helpful.