text: Asymptomatic COVID 19 infection diagnosis transmission population characteristics A novel coronavirus first discovered in late December 2019 has spread to many countries around the world An increasing number of asymptomatic patients have been reported and their ability to spread the virus has been proven This brings major challenges to the control of the transmission The discovery and control of asymptomatic patients with COVID 19 are the key issues in future epidemic prevention and recovery In this narrative review we summarise the existing knowledge about asymptomatic patients and put forward detection methods that are suitable for finding such patients Besides we compared the characteristics and transmissibility of asymptomatic patients in different populations in order to find the best screening diagnosis and control measures for different populations Comprehensive preventive advice is also provided to prevent the spread of infection from asymptomatic patients 