Specific anti‐CMV IgG antibodies were detected in 86.2% (50/58) and anti‐CMV IgM in 5.2% (3/58) of ME/CFS serum samples and in 88% (44/50) and 2% (1/50) of control samples, respectively. This evidence concerns the gene CD40LG and myalgic encephalomeyelitis/chronic fatigue syndrome.