The concept of scale politics offers historians a useful framework for analyzing the connections between environment and health. This essay examines the public health campaign around emerging diseases during the 1990s, particularly the ways in which different actors employed scale in geographic and political representations; how they configured cause, consequence, and intervention at different scales; and the moments at which they shifted between different scales in the presentation of their arguments. Biomedical scientists, the mass media, and public health and national security experts contributed to this campaign, exploiting Americans' ambivalence about globalization and the role of modernity in the production of new risks, framing them in terms that made particular interventions appear necessary, logical, or practical.