Epstein-Barr / herpesvirus reactivation
Reactivation of latent EBV (or other herpesviruses), associated with fatigue and neurocognitive symptoms.
Several studies report recent EBV reactivation (EA-D IgG or VCA IgM positivity) in roughly two-thirds of Long COVID patients versus ~10% of controls, concentrated in fatigue and neurocognitive phenotypes. The serology is cheap, so it is useful for phenotyping — but the association is not proven causation, and there is no completed randomized trial showing that antiviral treatment of EBV helps Long COVID. Valacyclovir is sometimes tried by analogy to ME/CFS work; valganciclovir/ganciclovir carry real toxicity (myelosuppression, nephrotoxicity) and should be approached cautiously given unproven benefit.
How it's tested
EBV antibody panel
VCA IgM and EA-D IgG titres indicating recent Epstein-Barr reactivation. Cheap and useful for phenotyping (association, not proof of causation).
Treatment options & their evidence
Graded honestly — including treatments that failed in good trials, which is worth knowing.
Valacyclovir (anti-herpesvirus)
Anecdotal onlyCautionTried by analogy to ME/CFS work; no completed Long COVID RCT, and nucleoside analogues have only modest activity against latent EBV.
Caution: Renal dose-dependent; the related valganciclovir/ganciclovir carry significant myelosuppression and nephrotoxicity — a real harm-vs-evidence mismatch.