It is possible to be infectious on the same day of contact with the new coronavirus. New coronavirus pneumonia is contagious during the incubation period, so it is possible to be infectious on the same day, and the strength of the contagiousness is related to the number of viruses, their virulence, and the infected person’s autoimmunity, among other factors. The incubation period of the new coronavirus pneumonia is about 1~14 days, and it is possible for the patient to become infectious during the incubation period, that is to say, if the incubation period of the patient is 1 day, then the virus has already multiplied in the patient’s body on the day of infection, and therefore the infectiousness can appear on the same day of the exposure to the new coronavirus. The infectiousness of the new coronavirus is related to the number of viruses, virulence, and the infected person’s autoimmunity, etc. If the number of infected viruses is high, the virulence of the new coronavirus strain is strong, and the infected person’s autoimmunity is weak, then the new coronavirus will reproduce in large numbers in the body, and will soon show strong infectiousness. If you come into contact with a person infected with the new coronavirus, you should contact your local community and epidemic prevention department as soon as possible, and cooperate with the epidemic prevention according to local policies. Tip: In this article, “new coronavirus pneumonia” and “new coronavirus pneumonia” were renamed to “new coronavirus infection” on December 26, 2022, as announced by the National Health Commission.