The epidemic situation in the United States deteriorated rapidly in a short time. On March 19, the number of confirmed cases in the United States exceeded 10000, and on March 21, it exceeded 20000. At present, there are more than 35000 cases. According to the New York Times, Columbia University researchers predict that if no control or only partial measures are taken, the peak number of newly confirmed cases in a single day in the United States may be as high as 300000 to 500000