People walk on the beach at Assateague Island National Seashore in Chincoteague Island, Virginia, the United States, on Feb. 20, 2021. Key indicators of COVID-19 transmission in the United States continue to fall, but health experts warn the public not to let down guard as the country sees uptick in coronavirus variants infections. (Xinhua/Ting Shen)

People walk on the beach at Assateague Island National Seashore in Chincoteague Island, Virginia, the United States, on Feb. 20, 2021. Key indicators of COVID-19 transmission in the United States continue to fall, but health experts warn the public not to let down guard as the country sees uptick in coronavirus variants infections. (Xinhua/Ting Shen)

People walk on the beach at Assateague Island National Seashore in Chincoteague Island, Virginia, the United States, on Feb. 20, 2021. Key indicators of COVID-19 transmission in the United States continue to fall, but health experts warn the public not to let down guard as the country sees uptick in coronavirus variants infections. (Xinhua/Ting Shen)