The Pandemic Arc: Expanded Narratives in the History of Global Health.

Using the examples of plague, smallpox, and HIV/AIDS, the present essay argues for the benefits of incorporating the evolutionary histories of pathogens, beyond visible epidemic spikes within human populations, into our understanding of what pandemics actually are as epidemiological phenomena. The pandemic arc - which takes the pathogen as the defining "actor" in a pandemic, from emergence to local proliferation to globalization - offers a framework capable of bringing together disparate aspects not only of the manifestations of disease but also of human involvement in the pandemic process. Pathogens may differ, but there are common patterns in disease emergence and proliferation that distinguish those diseases that become pandemic, dispersed through human communities regionally or globally. The same methods of genomic analysis that allow tracking the evolutionary development of a modern pathogen such as SARS-CoV-2 also allow us to trace pandemics into the past. Reconstruction of these pandemic arcs brings new elements of these stories into view, recovering the experiences of regions and populations hitherto overlooked by Eurocentric narratives. This expanded global history of infectious diseases, in turn, lays a groundwork for reconceiving what ambitions a truly global health might aim for.