The incubation period of pneumonia usually has no special symptoms. The period between the invasion of pathogens into the body and the onset of the disease is called the incubation period. Pneumonia caused by some viruses (e.g., influenza virus, novel coronavirus, etc.) may have an incubation period, which varies from 1 day to more than 10 days, e.g., the incubation period of the novel coronavirus ranges from 1 to 14 days. During this period, there may be no obvious clinical manifestations, but there is still the possibility of spreading the virus. The incubation period is the basis for judging the epidemic process, tracing the source of infection and speculating on the transmission route, which is helpful for diagnosis and the basis for formulating the quarantine period.