After an acute infection with SARS-CoV-2, a subset of individuals experience a persisting post-viral syndrome known as long COVID, featuring various symptoms including fatigue, post-exertional malaise and neurocognitive impairments. The underlying aetiology of long COVID and other post-viral syndromes is unclear, with several hypotheses being proposed, such as viral persistence, chronic inflammation, hypercoagulability and autonomic dysfunction. Now, a study identifies a mechanism that links all these hypotheses and may offer new opportunities for treatment.