People spend their Wednesday afternoon on the National Mall in Washington, D.C., the United States, Aug. 26, 2020. The U.S. Centers for Disease Control and Prevention (CDC) has changed its COVID-19 testing guidelines, no longer recommending testing for most people without symptoms. (Photos: Xinhua)

People spend their Wednesday afternoon on the National Mall in Washington, D.C., the United States, Aug. 26, 2020. The U.S. Centers for Disease Control and Prevention (CDC) has changed its COVID-19 testing guidelines, no longer recommending testing for most people without symptoms.

People spend their Wednesday afternoon on the National Mall in Washington, D.C., the United States, Aug. 26, 2020. The U.S. Centers for Disease Control and Prevention (CDC) has changed its COVID-19 testing guidelines, no longer recommending testing for most people without symptoms.

A man rides a bicycle near the Lincoln Memorial Reflecting Pool in Washington, D.C., the United States, Aug. 26, 2020. The U.S. Centers for Disease Control and Prevention (CDC) has changed its COVID-19 testing guidelines, no longer recommending testing for most people without symptoms.

People spend their Wednesday afternoon at the Lincoln Memorial in Washington, D.C., the United States, Aug. 26, 2020. The U.S. Centers for Disease Control and Prevention (CDC) has changed its COVID-19 testing guidelines, no longer recommending testing for most people without symptoms.

People spend their Wednesday afternoon on the National Mall in Washington, D.C., the United States, Aug. 26, 2020. The U.S. Centers for Disease Control and Prevention (CDC) has changed its COVID-19 testing guidelines, no longer recommending testing for most people without symptoms.

People spend their Wednesday afternoon at the Lincoln Memorial in Washington, D.C., the United States, Aug. 26, 2020. The U.S. Centers for Disease Control and Prevention (CDC) has changed its COVID-19 testing guidelines, no longer recommending testing for most people without symptoms.

People jog on the National Mall in Washington, D.C., the United States, Aug. 26, 2020. The U.S. Centers for Disease Control and Prevention (CDC) has changed its COVID-19 testing guidelines, no longer recommending testing for most people without symptoms.

People spend their Wednesday afternoon at the Lincoln Memorial in Washington, D.C., the United States, Aug. 26, 2020. The U.S. Centers for Disease Control and Prevention (CDC) has changed its COVID-19 testing guidelines, no longer recommending testing for most people without symptoms.