Asymptomatic infections are generally referred to as newly crowned asymptomatic infections, which do not have specific clinical manifestations and can only be detected by nucleic acid testing. Asymptomatic infected people are developed from the state of occult infection, which means that after the pathogen invades the body, it only induces the body to produce a specific immune response, but does not cause or only causes minor tissue damage, and thus does not clinically show any symptoms, signs, or even biochemical changes, which can only be detected by immunological examination. After the occult infection process is over, most people can acquire varying degrees of specific immunity with the help of the immune system, which can clear the pathogen. However, due to the low immunity of a small number of people can not completely clear the virus, ultimately leading to immunity and the virus are not able to change into a pathogenic carrier state, that is, the pathogen persists in the body, can achieve the transmission of the pathogen, become asymptomatic carriers, that is, asymptomatic infected people. Therefore, asymptomatic infected people do not have special manifestations of related diseases, and can only be mapped by nucleic acid testing in the population during epidemiological screening.