On January 30, 2006, Dr. Michael J. Klag, dean of the Johns Hopkins Bloomberg School of Public Health, convened a day-long symposium to examine the public health aspects of a potential pandemic like H5N1 avian influenza. The event brought together experts on every facet of the avian flu, to educate the wider community on what we know and don't know about this alarming disease. In Part 5, Nancy Kass, the Phoebe R. Berman Professor of Bioethics and Public Health at the Bloomberg School, discusses an ethics framework for considering public health responses to avian flu.