The article discusses the multiple forms of expertise articulated by a specific kind of digital influencer - online science communicators - during the COVID-19 pandemic in Brazil. Our case study focuses on the performance of Atila Iamarino, a PhD in Microbiology that achieved an unprecedented public recognition after predicting, in a YouTube live transmission, that more than a million people could die in the country due to the coronavirus. Assuming the relational and networked dimension of expertise, the article discusses how Atila combined and interchanged academic, affective, and sociotechnical abilities in his performances on social media and on other (media) institutions during a public health crisis marked by the lack of coordination and the political instrumentalization of science by the Brazilian federal government. The case study is based on a systematic observation of Atila’s accounts on YouTube and Twitter, and on additional material published from March to August 2020. In the conclusions, based on how the Brazilian science influencer managed his visibility, alliances, and scientific background during the radical uncertainty period, we highlight how the expertise was built based on conditions of possibility that emerged in Brazil during the pandemic, which reveals contemporary tensions between science, politics, media, and other epistemic institutions.
