NPR is reporting that some Wuhan residents in China who had tested positive earlier and then recovered from the disease are testing positive for the virus a second time . It's raising concerns of a possible second wave of cases, as China prepares to lift quarantine measures to allow residents to leave the epicenter of its outbreak next month. From the report:One theory is that they were first given a false negative test result. Another theory is that, because the test amplifies tiny bits of DNA, residual virus from the initial infection could have falsely resulted in that second positive reading.