Based on studies in South Korea, it's because the first tests are false positive, so "asymptomatic" really means "not infected" the first time. In cases in Sout

Based on studies in South Korea, it's because the first tests are false positive, so "asymptomatic" really means "not infected" the first time. In cases in South Korea where they were hospitalized, and then retest positive, it's because the second tests were false positive. So far no cases of getting truly sick again after resolving the first time (once they get to the bottom of initial/subsequent false positives).