Abstract In 1895, the crime-writing duo of L. T. Meade and Clifford Halifax, MD, published ‘A Doctor’s Dilemma’ in The Strand Magazine. In it, the young physician Arthur Feveral describes a recent influenza outbreak which has left an ‘extraordinary sequel . . . My health is gone—my nerve has deserted me’. Influenza plays a central role in this fiction, but Feveral’s story is simply one of many – documentary and fictionalized – that populate the pages of late nineteenth-century British periodicals. The ‘Russian’ influenza pandemic of 1889–1894 was the last great European outbreak of the nineteenth century, leaving in its wake such widely discussed neurological effects (neurasthenia, psychosis, and melancholy) that they earned their own nosography: ‘influenza nervosa’. This paper examines the pandemic’s enduring cultural and biosocial impact through the framework of sequelae – chronic conditions arising in the aftermath of acute illness. Drawing on medical case histories, criminal reports, illness narratives, and works of fiction, it explores how the Victorians taxonomized and theorized such long-term effects of infectious disease. First, sequelae became a category separate from ‘complications’, vital to broader preoccupations with prolonged illness, uncertainty, and moral and bodily weakness and degeneracy, and the Victorians scaffolded around it notions of vigour and debility, difference, predisposition, and heredity. Second, they domesticated and repurposed colonial and tropical theories of hygiene as explanatory frameworks. Through close readings of ‘long influenza’ in the clinic and in fiction, this paper also frames the kinds of narratives which gained especial purchase, and the sufferers deemed both susceptible and sympathetic. Finally, it argues that the acute phase of infectious anxiety gave way to a longue durée of sequelae, and that Victorian responses provide critical insights and warnings for our own era.