Surveillance is the radar of public health. Without tracking, often by name, the incidence and prevalence of both infectious and chronic disease, health officials would be unable to understand where and how to potentially intervene or what resources might be required to protect populations. Surveillance without individual informed consent has been challenged in the name of both bioethics and human rights. In this article we contend that a robust conception of public health not only justifies surveillance but, without disregarding the need to respect individuals, provides an affirmative duty to engage in surveillance. There may be social and political circumstances in which the names of those reported cannot be protected from unwarranted disclosure and misuse for ends that have little to do with protecting the public's health. But while the potential for misuse requires an ongoing, searching scrutiny of disease surveillance, remote or hypothetical threats should not serve to undermine this vital public health activity.