Long COVID and post-infectious syndromes: medicine still searching for answers

Millions are suffering — and medicine is still catching up

At ACR Convergence 2026, Cleveland Clinic immunologist Dr. Leonard Calabrese delivered a pointed message: patients with post-acute infectious syndromes — including long COVID, ME/CFS, and fibromyalgia-like conditions — are real, they are suffering, and they deserve to be taken seriously. Despite millions of documented cases worldwide, these conditions remain poorly defined, and no medical specialty has fully claimed ownership of them.

Calabrese argued that the longstanding habit of dismissing unexplained symptoms as psychological is outdated and harmful. Advances in neuroscience and neuroimmunology now point to dysfunction in integrated brain-immune networks as a plausible driver of these chronic conditions — a framework that could finally bridge the gap between "it's in your head" and "we can't find anything wrong."

Key Takeaways:

• ME/CFS overlaps with fibromyalgia in ~50% of cases, yet remains largely outside mainstream rheumatology
• Over 3 million Americans are estimated to have ME/CFS, with no specialty claiming clear ownership
• Long COVID has created an unprecedented opportunity to study post-infectious illness at scale
• Rheumatologists are well-positioned to lead, given their experience with immune dysregulation and nociplastic pain

Why it matters: Post-infectious syndromes represent a massive, underserved patient population. Without clearer definitions, clinical ownership, and research investment, millions risk being dismissed or mismanaged — a gap the medical community can no longer afford to ignore.