Can People with Asymptomatic or Pre-Symptomatic COVID-19 Infect Others: A Systematic Review of Primary Data

Asymptomatic but infectious people have been reported in many infectious diseases. Asymptomatic and pre-symptomatic carriers would be a hidden reservoir of COVID-19. Aim: This review identifies primary empirical evidence about the ability of asymptomatic carriers to infect others with COVID-19 pandemic and reflects on the implications for control measures. Methods: A systematic review is followed by a narrative report and commentary inclusion criteria were: studies reporting primary data on asymptomatic or pre-symptomatic patients, who were considered to have passed on COVID-19 infection; and published in indexed journals or in peer review between January 1 and March 31, 2020. Results: Nine articles reported on 83asymptomatic or pre-symptomatic persons. Conclusions: The evidence confirmsCOVID-19 transmission from people who were asymptomatic at the time. A series of implications for health service response are laid out.