According to news reports, Thomas E. Duncan, a 40-year-old Liberian national who was visiting relatives in Dallas, went to the emergency room at Texas Health Presbyterian Hospital on Sept. 25 with a complaint of fever and abdominal pain. A nurse, following a checklist, asked whether he had recently visited West Africa. He told her he had. "Regretfully, that information was not fully communicated," a hospital official said Wednesday. Mr. Duncan was then sent home with antibiotics — useless against the Ebola virus. (Of course, they would also be useless against the "low-grade common viral disease" the doctors thought he had.) He returned on the 28th, and by then he was reportedly vomiting profusely — a real worry since Ebola is spread through contact with the bodily fluids of an infected person. In the days when he was symptomatic and home, he had primary or secondary contact with scores of people, including five schoolchildren and the medics who transported him to the hospital. Now Texas health officials have put Mr. Duncan's family under mandatory quarantine and are monitoring as many as 100 people.