The role of co-infection in the pathogenesis of acute SARS-CoV-2 infection and development of post-acute sequelae: A perspective

A major health challenge resulting from the COVID-19 pandemic is the manifestation of post-acute sequelae of SARS-CoV-2 (PASC). PASC (or long COVID) is a collective term used for clinical symptoms, various pathologies, and life-quality-changing functional impairment that persist for months to years after the initial SARS-CoV-2 infection. The mechanisms underlying PASC are not understood, although advances have been made in identifying factors that may contribute to long-term pathology. Recent data have emerged, showing an association between SARS-CoV-2 viral persistence and non-SARS-CoV-2 infections (pre-existing, viral reactivation, or new infections) in facilitating or mediating PASC. However, the heterogeneous nature and timing of co-infections have made it challenging to understand, interpret, and contextualize their contribution to PASC. Here, we summarize the impact of potential viral, bacterial, and fungal infections on SARS-CoV-2 pathogenesis, with a focus on their possible roles in the development of PASC. We also provide a framework to understand the mechanisms of PASC and inform basic, translational, and clinical research initiatives, including RECOVER, a large and ongoing research initiative to understand, treat, and prevent long COVID.