Nearly half a million residents in the Chinese city where the novel coronavirus first emerged may have been infected with Covid-19 — almost 10 times its official number of confirmed cases, according to a study by the Chinese Center for Disease Control and Prevention. The researchers found an antibody prevalence rate of 4.43% for Covid-19 among residents in Wuhan, a metropolis of 11 million people. As of Sunday, Wuhan had reported a total of 50,354 confirmed cases of Covid-19, according to the Wuhan Municipal Health Commission. The results of the study were revealed in a Chinese CDC post on social media Monday. It did not mention whether the study has been published in academic journals.