Following its exceptional response to the 2003 severe acute respiratory syndrome (SARS) outbreak, the World Health Organization (WHO) gained new powers to securitise infectious disease outbreaks via the revised 2005 International Health Regulations (IHRs) and the ability to declare a Public Health Emergency of International Concern (PHEIC). This article investigates the declaration of a PHEIC in relation to the 2009 H1N1 flu pandemic, the 2014–16 Ebola outbreak, and the ongoing COVID-19 pandemic. It argues that the securitisation of these outbreaks was dependent upon global surveillance networks that utilised genetic technologies to visualise the molecular characteristics and spread of the pathogen in question. Genetic evidence in these cases facilitated the creation of a securitised object by revealing the unique and ‘untypable’ nature of the H1N1 and SARS-CoV-2 viruses and made visible the widespread prevalence of Ebola across the population of West Africa. The power of this evidence draws from a societal perception of science as producing objective ‘facts’ about the world that objectivise their objects of concern and empower political actors in the implementation of their security agendas. As a result, scientific evidence provided by genetic technologies now plays a necessary and indispensable role in the securitisation of infectious disease outbreaks.