Since the virus itself has no cellular structure, this dictates that it cannot survive on its own and must find a host. After monitoring by epidemiologists and virologists, it was found that the source of transmission of the novel coronavirus was basically determined to be wild animals. It may have spread from wild animals to humans in the early stages of transmission, but has now adapted to be in the human environment and has entered the stage of human-to-human transmission. From the current clinical epidemiological investigation, the source of infection is mainly pneumonia patients with novel coronavirus infection. The transmission is characterized by the absence of any typical symptoms during the incubation period while already being infectious. Moreover, there are also occult infected patients who have become infectious at the early stage when their body temperature is not high or normal.