DALLAS – Why a Valley Manor Rehabilitation Center resident – who had COVID-19, recovered and later received two vaccine doses – tested positive again for the virus is up to local officials to resolve, but an infectious disease expert, Dr. Murray Cohen, offered general thoughts on the topic. After having just reopened March 12, following a yearlong shutdown, the positive test forced the Excelsior Springs facility back into lockdown Monday. Cohen gave possible reasons for the positive test... • A person’s autoimmune system could be compromised. With diseases, such as HIV, a system breakdown could make getting rid of COVID-19 difficult, he said. • Another issue could be the virus never left the body. “It’s infrequent, but usually when it happens, it means that you never actually resolved the virus, that you’ve still got kind of a relapse of the same infection,” Cohen said. “Think about these folks that we call the ‘long haulers’ who continue to have symptoms long after they’ve…