More U.S. colleges were grappling with high numbers of students testing positive for the coronavirus just days into the start of the fall semester after some universities rolled back their campus reopening plans in recent weeks. The University of Alabama on Monday reported more than 550 people across its campuses had tested positive for COVID-19 since it resumed in-person classes on August 19. Most of those infected were students, faculty and staff at the university’s main campus in Tuscaloosa.