Haran, John P, Bradley, Evan, Zeamer, Abigail L et al. · JCI insight · 2021 · DOI
This study looked at bacteria in the mouth of people with COVID-19 to understand why some people develop long COVID. Researchers found that people with long COVID had higher levels of inflammation-causing bacteria, particularly types called Prevotella and Veillonella. Interestingly, the oral bacteria patterns in long COVID patients resembled those seen in chronic fatigue syndrome patients, suggesting the microbiome may play a role in prolonged illness.
This research provides evidence that oral microbiome dysbiosis may contribute to long COVID, a condition that shares clinical features with ME/CFS. Understanding microbial drivers of prolonged inflammation could open new diagnostic and therapeutic avenues for both long COVID and ME/CFS patients, potentially through targeted microbiome interventions.
This study demonstrates association, not causation—it does not prove that dysbiosis causes long COVID symptoms or that restoring the microbiome would resolve illness. The study also does not establish whether microbiota changes are a cause, consequence, or epiphenomenon of prolonged infection. Additionally, findings from one microbiome compartment (oral) may not reflect systemic dysbiosis.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
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