Field Guide
Long COVID & Post-Viral Syndrome
Persistent multi-system symptoms — fatigue, brain fog, exercise intolerance, autonomic dysfunction, breathlessness — that continue for months after an acute viral infection (COVID-19, EBV, enterovirus, influenza). Functional medicine looks at mitochondrial injury, viral persistence, immune dysregulation, mast cell activation, and autonomic (POTS-like) overlap.
Long COVID is like your operating system never fully rebooted after the crash. Programs run in the background, batteries drain fast, and pushing the machine makes it freeze.
In plain English
Long COVID (post-acute sequelae of SARS-CoV-2) is a persistent multi-system illness where symptoms continue for months after the acute infection. It shares mechanisms with other post-viral syndromes triggered by EBV, enterovirus, and influenza.
Research points to several overlapping drivers: viral persistence (fragments in tissue), mitochondrial injury, immune dysregulation and autoantibodies, mast cell activation, autonomic nervous system injury (POTS-overlap), and microclotting affecting oxygen delivery.
Hallmark symptoms are fatigue, post-exertional malaise (crash 24–72 hours after even mild activity), brain fog, air hunger, heart racing on standing, new sensitivities, and sleep and temperature disruption. Pacing — staying below your crash threshold — is the single most important early intervention.
Where you feel it
The step-by-step
- 1Acute infection
SARS-CoV-2 (or other virus) triggers widespread inflammation and mitochondrial stress.
- 2Failed resolution
Immune system doesn't fully clear the pathogen; autoantibodies and viral fragments persist.
- 3Multi-system injury
Mitochondria, autonomic nerves, mast cells, and endothelium all take damage.
- 4Chronic state
Fatigue, PEM, POTS-overlap, MCAS-like reactions, cognitive symptoms persist for months.
Symptoms, causes & labs
- Fatigue and post-exertional malaise (crashes after mild activity)
- Brain fog, poor recall, word-finding trouble
- Air hunger, exercise intolerance, heart racing on standing
- New food/scent sensitivities, loss or distortion of smell/taste
- Sleep disruption, temperature dysregulation
- Viral persistence (spike protein, EBV reactivation)
- Mitochondrial injury and impaired energy production
- Immune dysregulation, autoantibody formation, MCAS-like activation
- Autonomic nervous system injury (POTS-overlap)
- Microclotting and endothelial dysfunction
- 10-minute NASA lean test or tilt-table test
- EBV panel, comprehensive viral reactivation panel
- hs-CRP, D-dimer, fibrinogen, ferritin
- Comprehensive thyroid, morning cortisol, B12, vitamin D
- Small-fiber neuropathy / autoimmune workup where indicated
Common lifestyle changes that help
These are the foundational shifts most often used alongside clinical care for this pattern. Start with one; layer in the next only when the first feels automatic. Discuss anything major with your practitioner.
- AGGRESSIVE pacing — stay under your energy envelope; PEM sets recovery back weeks
- Rest is treatment, not laziness. Lie down before you need to
- Anti-inflammatory whole-food diet; low-histamine if reactive
- Address POTS-like symptoms with salt, fluids, compression
- Breathwork, vagus-nerve stimulation, and nervous-system regulation daily
Red flags — don't wait
- Chest pain, severe shortness of breath, or new arrhythmia
- Blood clot symptoms (leg swelling, one-sided weakness, sudden headache)
- Rapidly progressive cognitive decline
Supportive habits to discuss
- Pace strictly — the 'stop before you feel tired' rule; use a heart-rate cap
- Screen for POTS (NASA lean test), MCAS, and reactivated EBV
- Work with a Long COVID-literate clinician — this is a rapidly evolving field
Is this pattern showing up in your body?
Take our physician-designed assessment — 8 minutes, 80 questions across 25 root-cause categories.
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Medical disclaimer
This page is educational only. It is NOT medical advice, diagnosis, or treatment. Do not self-treat based on the information here. If you have symptoms, consult a licensed healthcare professional.