This dissertation examines the ways in which the ‘truth’ about an outbreak of zoonotic disease stabilises through the labour of sampling animals. While scarcely any case of Ebola had ever been reported in West Africa, the deadliest epidemic to date started in 2013 in the southeastern region of Guinea called ‘Forest Guinea’. Since then, ecologists and virologists from Africa, America and Europe have been conducting the largest investigation into what some frame as the origins of Ebola: they are trying to establish a fuller picture of the processes by which the disease is maintained and infects humans in a place that has become known as one of its ‘hotspots’. During 16 months of ethnographic fieldwork, I closely tracked the Guinean staff of one of those foreign projects – local vets who professionally defined their role as préleveurs (‘samplers’ in English) – while they captured animals, took, and dispatched fluid samples, communicated about the risks of contact with bats, and disclosed the finding of a new species of Ebola virus in bat species. The social sciences have dismantled the idea of singular, hegemonic epidemic origins, and indicated that complex sociospatial conditions allow for epidemics to emerge. This dissertation adopts a different analytical angle and outlines the technological, epistemological, and affective consequences of framing microbiological research as a search for the origin of epidemics. It focuses on the economy of knowledge, epistemological labour, and ethical aspirations of animal préleveurs, whose work is to make a hotspot exist in Forest Guinea. By combining attention to history, the scientific literature and ethnographic fieldwork, I resituate animal sampling within a West African genealogy of asymmetrical extraction and conservation, which crosscuts the colonial sciences, interwar disease ecology, global health, outbreak preparedness, and the newer One Health agenda. At the core of this multifaceted sampling enterprise is an interdependence between anticipatory practices and forms of insecurity – political, economic, environmental. The thesis suggests that insecurity is normalised by hotspot investigations, and that associated social hierarchies, causalities and moralities inflect the local notion of responsibility for the epidemic. Ultimately, insecurity configures the production of evidence about the so-called reservoir of Ebola and leads the hypothesis of a bat origin to gain strength in Guinea. The dissertation chapters foreground the controversies, dissimulation practices, fear, and cynicism that the quest for epidemic origins elicits locally, even as it contributes to imposing a single narrative for disease causality. In so doing, I challenge a social science view that scientific claims become authoritative when the institutions and practices that manufacture them are socially recognised as trustworthy and legitimate, i.e., secure. Instead, insecurity is entangled in the material performances and ethos of préleveurs. Far from only producing scientific evidence for experts, their activity generates clues about Ebola’s origins for many people in Guinea and Africa more generally – with significant consequences for research priorities and prevention policies.