Medical workers carry a patient from an ambulance to George Washington University Hospital in Washington D.C., the United States, on April 27, 2020. Global confirmed COVID-19 cases topped 3 million on Monday, reaching 3,002,303 as of 1 p.m. (1700 GMT), according to the Center for Systems Science and Engineering (CSSE) at Johns Hopkins University. (Photos: Xinhua)

Medical workers carry a patient from an ambulance to George Washington University Hospital in Washington D.C., the United States, on April 27, 2020. Global confirmed COVID-19 cases topped 3 million on Monday, reaching 3,002,303 as of 1 p.m. (1700 GMT), according to the Center for Systems Science and Engineering (CSSE) at Johns Hopkins University.

Medical workers carry a patient from an ambulance to George Washington University Hospital in Washington D.C., the United States, on April 27, 2020. Global confirmed COVID-19 cases topped 3 million on Monday, reaching 3,002,303 as of 1 p.m. (1700 GMT), according to the Center for Systems Science and Engineering (CSSE) at Johns Hopkins University.

Medical workers carry a patient from an ambulance to George Washington University Hospital in Washington D.C., the United States, on April 27, 2020. Global confirmed COVID-19 cases topped 3 million on Monday, reaching 3,002,303 as of 1 p.m. (1700 GMT), according to the Center for Systems Science and Engineering (CSSE) at Johns Hopkins University.

A medical worker wheels a patient from an ambulance to George Washington University Hospital in Washington D.C., the United States, on April 27, 2020. Global confirmed COVID-19 cases topped 3 million on Monday, reaching 3,002,303 as of 1 p.m. (1700 GMT), according to the Center for Systems Science and Engineering (CSSE) at Johns Hopkins University.