This Information, Communication, and Society paper (cowritten with Phillip Roth and Alin Olteanu) uses the work of Tarde and Deleuze and Guattari to understand contagion in the Information Age to be simultaneously biomedical and social. We focus specifically on the COVID-19 pandemic and the category of long COVID, and argue that the spread of fear and frustration about unexplained symptoms and the desire for inclusion in mainstream medicine on social media was integral to mobilization that led to the legitimization of the category. We propose broadening conceptions of ‘what spreads’ and helps structure collective and individual understandings of disease in a pandemic.