When I was coordinating the U.S. response to Ebola in the fall of 2014, one frequent problem was false reports of Ebola cases in this country. Early symptoms of Ebola resemble flu. Even when we screened out the 99% of flu patients who had not been to Liberia, Sierra Leone, and Guinea (and therefore did not have Ebola), there were still many more suspected or feared cases than actual instances of Ebola in the U.S. Many sleepless nights in the winter of 2014-2015 ended, fortunately, with negative Ebola tests. But among the many reasons policy makers and citizens are not...