"In the spring semester 2003, not long after we began to write this book, three of us taught an undergraduate honors seminar designed to explore ethics is­ sues in infectious disease. It was January when the course began, and we found a group of eager, well-prepared, advanced honors students, many of whom expected to enter medical school. We covered the basics of ethical theory and the microbiology of infectious disease. We read famous cases in the annals of public health. We discussed dilemmas of medical management and the obliga­ tions of the physician, especially in times of plague. But we also found our­ selves mentioning a few reports coming from the Centers for Disease Control and Prevention-this was in early January 2003-of a couple of cases of a previously unrecognized syndrome, trickling in from China. We did not pay much attention to it in the first week or two of class, while we were learning the basic science of infectious disease, how various viruses function, and by what mechanisms human-to-human and animal-to-human transmission occurs. We had read about classic problems like the plague in Greece at the time of Thucydides and in medieval Europe, but those were problems of the past whose only contemporary analogue was AIDS. But those new cases kept trickling in-there were a handful of cases when the class met one week, and a few dozens of cases when it met a week later, and cases in the hundreds when it met the week after that. At the beginning, although the new condition had been given a name, Severe Acute Respiratory Syndrome or SARS, nobody knew how to stop it or treat it. It was spreading, and often with fatal outcome. Many of the members of the class were pre-med students. As the number of SARS cases grew, it was becoming clear that this devastating disease af­ fected health-care workers with unusual frequency. Now the class was becom­ ing more than academic, and much more serious: "do physicians have an obli­ gation to treat patients with potentially lethal infectious diseases?" we wondered. Some argued yes, appealing to codes of ethics from the AMA and elsewhere; some argued no, reminding us that the risk to themselves might also be a risk to their spouses and their children. Meanwhile, the strength of the SARS epidemic was increasing, with new cases reported not just in China but next door, in Toronto, on this continent, just a short plane ride away.We still did not know how far it would go or how to stop it. What precautions ought a society take against a disease whose causes and mechanism are still poorly understood? Now the class debated the ethics of universal involuntary quarantine for anyone exposed, state-required im­ munization if a vaccine were ever to be developed, and issues of distributive justice about who should get first access to treatment and how health-care re­ sources should be prioritized. We were all scared, students and teachers alike, because we understood all too fully what could be at stake and how deeply troubling the moral issues it raised were. As the seminar continued, we all felt the sense of vulnerability that we would later come to associate with what we call "embeddedness" in a "web" of infectious disease -that sense of threat, an unknown peril, a potential disas­ ter, from a new and not-yet-understood disease breaking out among human­ kind. And we began to think more seriously about the ethical issues in infec­ tious disease, not merely as an academic exercise in an honors class but as a deeply disturbing human issue. Fortunately, SARS was contained shortly afterward, at least as far as we currently know. Just the same, none of us, we think, will forget this class: this was physicians and prospective physicians and ethicists working together in real life, in real time, to try to address issues of compelling personal and social concern. This book is in part the fruit of these reflections"--