RESUMO
This article explores the entangled histories of dengue and yellow fever. It traces how historical conflations of these diseases deepened at the start of the twentieth century in the context of rising fears that yellow fever might spread to Asia. Advances in biomedicine, I suggest, reinforced notions of their kinship and generated competing theories that dengue either foreshadowed yellow fever in Asia or inoculated the region against it. This history in which the language and science of dengue and yellow fever shadowed one another offers a nonlinear narrative of scientific progress. Furthermore, as the so-called neglected tropical diseases resurge in the present, it elucidates how disease threats are read against one another. Thus, the article offers a historical context to ongoing discussions on disease emergence and pandemic preparedness.