Historians generally view the growth of global governance in disease control as the product of world capitalist expansion and empire building in the late nineteenth and early twentieth centuries. This article uses the world of a U.S. consul, Etienne Cathalan Jr. (1757–1820), to reexamine when, where, and how diplomacy and statecraft participated in the creation of long-distance medical relations and health policies. During Cathalan’s era, when trade and naval warfare expanded dramatically beyond Europe and into the Atlantic world, European and American polities regarded the networks of commerce as a rich resource for intelligence, international relations, and knowledge about the natural world. To preserve and extend trade and influence, they built far-flung networks of commercial agents and consuls, like Cathalan, who could broker relations and information in and between foreign ports of call. Health matters became tangled up in the preservation of shipping and commercial relations during Cathalan’s tenure. Fluctuating patterns in trade and naval conflict introduced new ecological and health cultural interactions among Americans, Mediterranean Europeans, and populations along the North African coast. Together with government agents, seafarers, and physicians, Cathalan transformed his powers, administrative skills, and sociocultural capital into resources for surveying disease and mediating new health relations in the Atlantic and Europe.