The incubation period is also known as the asymptomatic period in the staging of infectious diseases, which refers to the pathogen infecting the human body, parasitized in a certain part of the body, due to the body’s immune function is sufficient to limit the pathogen without causing overt infection, but at the same time the immune function is not sufficient to remove the pathogen, the pathogen is latent for a long period of time, and then when the immune function of the body decreases, it causes an overt infection. Therefore, whether an infectious disease develops or not depends mainly on the pathogenicity of the pathogen and the immune function of the body. Latent infections do not exist in every infectious disease. Common latent infections include herpes simplex virus infection, herpes zoster rash virus infection, malaria, and tuberculosis.