This dissertation is an ethnographic and historical study of nurses’ knowledge-making practices in the face of the prolific uncertainties engendered by global epidemics and pandemics and their aftermath in Toronto, Canada, where the 2003 SARS epidemic is built into the very foundations of health care policy, practice, and infrastructure. Working at the intersection of feminist science studies and medical anthropology, this dissertation moves from the 2003 SARS epidemic in Toronto to the COVID-19 pandemic of the early 2020s to trace nurses’ lived experiences and knowledge-making practices in relation to the uncertain exposures proliferated during moments of crisis and in their aftermath. Embedded in the institutional and political environment of Ontario’s social welfare system, this dissertation further attends to how close proximity to patients, a key element of nursing work, places nurses in the midst of the movement of viruses and the precarious, transitive uncertainties that emerge with them which demand what I term “hap-hazard knowledges,” or highly specialized, situated, and specific forms of knowledge production that cannot be divorced from nurses’ experiences and risks of illness, injury, and violence in hospital settings. This dissertation traces how pervasive discourses on nurses’ heroism and sacrifice early in the COVID-19 pandemic also shifts nurses’ experiences and exposures—managing, navigating, and reducing them—from a collective effort to an individual responsibility for limiting the risk to selves, loved ones, and patients. Examining the aftermath, this dissertation further explores Ontario’s workers’ compensation policies, and particularly the reconfiguration of conditions like Posttraumatic Stress Disorder (PTSD) as workplace injuries, as they have become sites of contestation over nurses’ working conditions and the limits of professional identity and practice. Opening up how PTSD structures inquiries into what does and does not constitute normal, everyday, and unexceptional work, this dissertation attends to how PTSD can serve as a normative force through which certain kinds of exposures become naturalized and unexceptional. As extraordinary events recede into everyday life as part of the “new normal,” and previously problematic working conditions are reconstituted and normalized, this dissertation provides a critical contribution to understanding how certain aspects of professional identities, knowledge, and skills are reshaped, reconstituted, and naturalized, even as it also opens up questions of the depth of knowledge, techniques, and skills that fundamentally shape “caring professions” like nursing.