China’s reversal on its Zero COVID Policy has produced a wave of infection that has overwhelmed many hospitals. Research published in Chinese state media suggests more than 900 million people in the country were likely infected with COVID in a wave that peaked nearly two weeks after restrictions were lifted. Symptoms can persist beyond the initial infection, lasting for weeks, months, or even years. Dr. Francesca Beaudoin, director of the Long COVID Initiative at Brown University, joins Hari Sreenivasan to explain why the disease is so difficult to diagnose.