Concerns about health and disease have long pervaded mathematics education research, yet their implications have been underappreciated. This article focuses on three contemporary relationships amplified by the COVID-19 pandemic: (1) school mathematics and national health; (2) mathematics educators' roles in distinguishing the health needs of students; and (3) mathematics instruction as either enhancing or threatening students' mental health and social adjustment. We argue that these concerns are foundational preoccupations of mathematics education research that have persistently shaped debates over who should learn mathematics, how, and to what ends. Our study examines histories of school mathematics and health discourses to explore how particular notions of health entered US mathematics education during the 19th and early twentieth centuries in ways that resonate with recent research trends and responses to COVID-19. We especially attend to how health/pathology distinctions reconfigured hierarchies of nationality, sex, race, and dis/ability within exclusionary, segregated, colonial, and tracked mathematics instruction. By mapping some of the shifting contours of health and pathology over time, we emphasize the potential dangers of the pandemic reanimating long-circulating dividing practices, such as in emerging trends comparing national metrics of well-being, responding to perceived trauma with differentiated instruction, and seeking to calibrate healthy mathematics identities in marginalized groups.