FILE - A photographer on a tall ladder tries to take photos of the World Health Organization convoy after it entered the Huanan Seafood Market on the third day of field visit in Wuhan in central China's Hubei province on Jan. 31, 2021. The hunt for COVID-19 origins has gone dark in China. An AP investigation drawing on thousands of pages of undisclosed emails and documents and dozens of interviews found feuding officials and fear of blame ended meaningful Chinese and international efforts to trace the virus almost as soon as they began, despite years of public statements to the contrary. (AP Photo/Ng Han Guan, File)
FILE - A security person moves journalists away from the Wuhan Institute of Virology after a World Health Organization team arrived for a field visit in Wuhan in China's Hubei province on Feb. 3, 2021. The hunt for COVID-19 origins has gone dark in China. An AP investigation drawing on thousands of pages of undisclosed emails and documents and dozens of interviews found feuding officials and fear of blame ended meaningful Chinese and international efforts to trace the virus almost as soon as they began, despite years of public statements to the contrary. (AP Photo/Ng Han Guan, File)
FILE - Peter Ben Embarek of a World Health Organization team attends a joint press conference at the end of their mission to investigate the origins of the coronavirus pandemic in Wuhan in central China's Hubei province on Feb. 9, 2021. The hunt for COVID-19 origins has gone dark in China. An AP investigation drawing on thousands of pages of undisclosed emails and documents and dozens of interviews found feuding officials and fear of blame ended meaningful Chinese and international efforts to trace the virus almost as soon as they began, despite years of public statements to the contrary. (AP Photo/Ng Han Guan, File)
FILE - A policeman moves journalists back from a farewell event held for the last group of medical workers who came from outside Wuhan to help the city during the coronavirus outbreak in Wuhan in central China's Hubei province on April 15, 2020. The hunt for COVID-19 origins has gone dark in China. An AP investigation drawing on thousands of pages of undisclosed emails and documents and dozens of interviews found feuding officials and fear of blame ended meaningful Chinese and international efforts to trace the virus almost as soon as they began, despite years of public statements to the contrary. (AP Photo/Ng Han Guan, File)
FILE - A security person moves journalists away from the Wuhan Institute of Virology after a World Health Organization team arrived for a field visit in Wuhan in China's Hubei province on Feb. 3, 2021. The hunt for COVID-19 origins has gone dark in China. An AP investigation drawing on thousands of pages of undisclosed emails and documents and dozens of interviews found feuding officials and fear of blame ended meaningful Chinese and international efforts to trace the virus almost as soon as they began, despite years of public statements to the contrary. (AP Photo/Ng Han Guan, File)
FILE - A volunteer looks out near a Chinese national flag during a farewell ceremony for the last group of medical workers who came from outside Wuhan to help the city during the coronavirus outbreak in Wuhan in central China's Hubei province on April 15, 2020. The hunt for COVID-19 origins has gone dark in China. An AP investigation drawing on thousands of pages of undisclosed emails and documents and dozens of interviews found feuding officials and fear of blame ended meaningful Chinese and international efforts to trace the virus almost as soon as they began, despite years of public statements to the contrary. (AP Photo/Ng Han Guan, File)
FILE - A security guard waves for journalists to clear the road after a convoy carrying the World Health Organization team entered the Huanan Seafood Market on the third day of a field visit in Wuhan in central China's Hubei province on Jan. 31, 2021. The hunt for COVID-19 origins has gone dark in China. An AP investigation drawing on thousands of pages of undisclosed emails and documents and dozens of interviews found feuding officials and fear of blame ended meaningful Chinese and international efforts to trace the virus almost as soon as they began, despite years of public statements to the contrary. (AP Photo/Ng Han Guan, File)
FILE - A farewell ceremony is held for the last group of medical workers who came from outside Wuhan to help the city during the coronavirus outbreak in Wuhan in central China's Hubei province on April 15, 2020. The hunt for COVID-19 origins has gone dark in China. An AP investigation drawing on thousands of pages of undisclosed emails and documents and dozens of interviews found feuding officials and fear of blame ended meaningful Chinese and international efforts to trace the virus almost as soon as they began, despite years of public statements to the contrary. (AP Photo/Ng Han Guan, File)
FILE - Marion Koopmans, right, and Peter Ben Embarek, center, of the World Health Organization team say farewell to their Chinese counterpart Liang Wannian, left, after a WHO-China Joint Study Press Conference at the end of the WHO mission in Wuhan, China, on Feb. 9, 2021. The hunt for COVID-19 origins has gone dark in China. An AP investigation drawing on thousands of pages of undisclosed emails and documents and dozens of interviews found feuding officials and fear of blame ended meaningful Chinese and international efforts to trace the virus almost as soon as they began, despite years of public statements to the contrary. (AP Photo/Ng Han Guan, File)