Conclusion
Nowadays, Coronavirus Disease 2019 (COVID-19) is rampaging though the world. Finding the source of infection and cutting off transmission are important measures to control COVID-19 before the effective vaccine is developed. However, as the epidemic progressed overtime, more and more asymptomatic cases brought huge challenges to the control of COVID-19. This review provides relatively comprehensive and updated information about asymptomatic cases of COVID-19. Further research into the prevalence of asymptomatic infection of COVID-19 is necessary to guide epidemic control efforts. All countries in the world should raise public awareness of protection and strengthen social security measures to prevent second outbreak caused by asymptomatic infection.