SARS 2003 is a coronavirus infection, which has similarities with the novel coronavirus in that the site of infection is in the lungs and the mode of transmission is through the respiratory tract. 2003 SARS had a relatively rapid onset, relatively short incubation period, relatively high fever, and a relatively large number of seriously ill patients. In retrospective analysis, the morbidity and mortality rate of SARS in 2003 was close to 10%, while the official report of novel coronavirus pneumonia was not high, the disease was relatively mild, and the incubation period was relatively long, with an average of 7 days and a long incubation period of 10-12 days, which made it more transmissible due to the long incubation period and mild symptoms. The transmission coefficient is 2.2, basically one person can spread to at least two people, the fever is not as heavy as SARS, and the overall mortality rate is lower than SARS. Therefore, this incidence is characterized mainly by high infectivity and low lethality. These two diseases from the clinical manifestations seen so far compared with the previous SARS, the disease is relatively less severe and more transmissible. Content source: Dr. You Lai