Historians have written copiously about the shift to ‘germ theories’ of disease around the turn of the twentieth century, but in these accounts an entire continent has been left out: Antarctica. This article begins to rebalance our historiography by bringing cold climates back into the story of environmental medicine and germ theory. It suggests three periods of Antarctic (human) microbial research – heroic sampling, systematic studies, and viral space analogue – and examines underlying ideas about ‘purity’ and infection, the realities of fieldwork, and the use of models in biomedicine. It reveals Antarctica not as an isolated space but as a deeply complex, international, well-networked node in global science ranging from the first international consensus on pandemic-naming through to space flight.