FILE - A resident from the Alexandra township gets tested for COVID-19 in Johannesburg, South Africa, Wednesday, April 29, 2020. In a new analysis released Thursday, April 7, 2022, the U.N. health agency reviewed 151 studies of COVID-19 in Africa based on blood samples taken from people on the continent between January 2020 and December 2021. WHO said that by last September, about 65% of people tested had some exposure to COVID-19, translating into about 800 million infections. In contrast, by that time, only about 8 million cases had been officially reported to WHO. (AP Photo/Jerome Delay, File)