BOSTON — Harvard Medical School will be hosting a symposium to explore the state of the opioid crisis and ways to stem it.The school says a panel of medical experts will be joined by Massachusetts Gov. Charlie Baker for the Tuesday event at the medical school's campus in Boston.Panelists will include professors and physicians including George Daley, dean of the medical school, and Bertha Madras, a professor who serves on a White House commission on opioids.