Troubling headlines have been cropping up across Asia: Some patients in China, Japan and South Korea who were diagnosed with COVID-19 and seemingly recovered have been readmitted to the hospital after testing positive for the virus again. Because SARS-CoV-2, the novel coronavirus that causes COVID-19, was only discovered a few months ago, scientists are still trying to answer many big questions related to the virus and the disease it causes. Among them is whether patients can be reinfected by the virus after they seem to recover from the symptoms. With other coronavirus strains, experts say the antibodies that patients produce...