The infectious agents of novel coronavirus pneumonia are infected persons and asymptomatic carriers. Asymptomatic carriers, i.e. persons with latent infection, do not show symptoms but have high viral loads and are contagious. The intermediate or natural host of the virus has not been identified, and it is currently thought to be most likely to be present in bats, in which many coronaviruses genetically similar to the novel coronavirus have been found, but not identical. There may also be intermediate hosts, such as pangolins, turtles, snakes, etc., but none of them have been confirmed, and no animal has yet been found to carry viruses identical to the novel coronavirus, i.e., the true intermediate host has not yet been found. The earliest source of infection for the outbreak is only speculative, not necessarily at the South China Seafood Market in Wuhan, or even in Wuhan, not necessarily China, and there may be other places of origin. Source: Dr. Yurai