But, when facing a disease that kills up to 70% of those who are infected, and no accepted treatment yet exists, patients could reasonably refuse consent to a trial in which they might receive a placebo, rather than an experimental treatment that offers some hope of recovery. In such cases, it might be more ethical to monitor carefully the outcomes of different treatment centers now, before experimental treatments become available, and then compare these outcomes with those achieved by the same centers after experimental treatments are introduced.