The Keystone Symposium meeting scheduled for 2025-2026, on 'Long COVID and Other Post-Acute Infection Syndromes,' will assemble global experts from various fields to explore critical dimensions of these debilitating conditions. The symposium aims to delve into challenges and potential solutions for achieving a consensus on clinical phenotypes, diagnostic criteria, diagnostic biomarkers, clinical trial design and endpoints, and treatments. Addressing the epidemiology of long COVID, the discussions will encompass demographics and comorbidities that influence both risk and recovery. Employing machine learning methodologies to identify symptom clusters biological signatures and potential treatments will contribute to unraveling the multifaceted nature of Long COVID. Exploring underlying heterogeneity of disease mechanisms, the meeting will cover persistent SARS-CoV-2 infection, autoimmunity, microbiome dysbiosis, latent virus reactivation, chronic inflammation, metabolic, autonomic and endocrine abnormalities, organ damage, coagulation, and immune deviation. Advances made in both clinical studies and animal models of long COVID will be discussed. A potential connection between long COVID and neurodegenerative diseases will be examined. Exploration into the pathophysiology of PAIS will provide key insights into the disease pathogenesis and potential avenues for therapy. The symposium will shed light on overlaps and distinctions between long COVID, ME/CFS, post-Lyme disease, and other PAIS, seeking common clinical phenotypes, underlying disease mechanisms and therapeutic targets. Furthermore, the meeting will spotlight ongoing and upcoming clinical trials, underscoring their pivotal role in advancing the understanding of disease mechanisms, therapeutic options, and enhancing outcomes for individuals living with Long COVID and PIAS. Our ultimate objective is to catalyze collaborative interactions among researchers, clinicians, and patients from diverse backgrounds, fostering a proactive and accelerated approach to unraveling the complexities of Long COVID and other PAIS, and formulating effective strategies for diagnosis, treatment, and care.