https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2787098
COVID-19, the disease caused by SARS-CoV-2, was first reported in December 2019.1 Globally, as of January 28, 2021, there have been 100 455 529 confirmed cases, including 2 166 440 deaths.2 The disease course of COVID-19 ranges from asymptomatic to mild respiratory infections to pneumonia and even to acute respiratory distress syndrome.3
Patients with no symptoms at screening point were defined as having asymptomatic infections, which included infected people who have not yet developed symptoms but go on to develop symptoms later (presymptomatic infections), and those who are infected but never develop any symptoms (true asymptomatic or covert infections).4,5
Owing to the absence of symptoms, these patients would not seek medical care and could not be detected by temperature screening. Presymptomatic transmission will also make temperature screening less effective.6 Only extensive testing and close contact tracing could lead to identification of more asymptomatic infections.7
Meanwhile, the highest viral load in throat swabs at the time of symptom onset indicated that infectiousness peaked on or before symptom onset.9 Moreover, studies showed that asymptomatic infections might have contributed to transmission among households, nursing facilities, and clusters.10-13
As the pandemic has been contained in many countries and regions, travel restrictions have been lifted and public places have reopened. Asymptomatic infections should be considered a source of COVID-19 infections that play an important role in the spread of the virus within community as public life gradually returns to normal. The management of asymptomatic carriers was essential for preventing cluster outbreaks and transmission within a community.
Thus, we conducted a meta-analysis to better understand the global percentage of asymptomatic infections among the tested and confirmed COVID-19 populations. Our results could be useful for strategies to reduce transmission by asymptomatic infections.