FILE - In this April 4, 2020, file photo, residents wearing masks stand in front of flowers placed near the Heroes Memorial Monument after a national moment of mourning for victims of coronavirus in Wuhan in central China's Hubei Province. A 10-member team of international researchers from the World Health Organization hopes to find clues as to the origin of the coronavirus pandemic in the central Chinese city of Wuhan where the virus was first detected in late 2019. (AP Photo/Ng Han Guan, File)