High-throughput 16S rRNA gene sequencing reveals alterations of intestinal microbiota in myalgic encephalomyelitis/chronic fatigue syndrome patients

43 Patients and 36 controls from Belgium and Norway were included in the study. Gut flora composition differed between people from different geographical origins. Significant alterations of gut microbiota composition were observed in patients.

This is relevant because 70% of all immune cells are located in the gastro-intestinal tract. Increased intestinal permeability may explain the systemic inflammatory situation in CFS.
Excess d-lactic acid production could contribute to mitochondrial dysfunction, but also to neurocognitive impairments in patients, since d-lactic acidosis is known to affect CNS function.

The predominance of women among patients, the fact that disease symptoms change upon e.g. puberty, pregnancy and menopause, has long suggested an involvement of hormones in ME/CFS. ER β, the preferred receptor of equol, is down-regulated in patients.
Disruption of estrogen signaling is consistent with some dysfunctions observed in ME/CFS. It could be related, for instance, with immune dysregulation since isoflavones, and more specifically equol, induce expression of antioxidant enzymes, and exert an anti-inflammatory action. Another potentially relevant aspect of phytoestrogens and their metabolites is their capacity to regulate vitamin D receptor activity, and vitamin D synthesis. The vitamin D system is critical for maintenance of gut mucosal immunity.Vitamin D has also been shown to modulate some processes that are critical for prevention of mucosal inflammation. One of the things not known yet is if the altered gut microbiota are cause or result of CFS.

Detection of Herpesviruses and Parvovirus B19 in Gastric and Intestinal Mucosa of Chronic Fatigue Syndrome Patients

Detection of Herpesviruses and Parvovirus B19 in Gastric and Intestinal Mucosa of Chronic Fatigue Syndrome Patients

They tested 48 CFIDS patients and 35 healthy controls.
For EBV, HHV6, HHV7 there were no big differences between patients and controls .
These virusses are probably not relevant for CFS.

Parvovirus B19 DNA was detected in 40% of the patients, and in less than 15% of the controls.
Parvovirus B19 may be involved in the pathogenesis of CFS, at least for a subset of patients.