Just like the other main viruses liked to ME/CFS (namely EBV, HHV-6, CMV, enteroviruses and parvovirus B19), studies have shown that ME/CFS patients more frequently have high titers to HHV-7 compared to healthy controls. These high titers suggest active infection, and thus implicate HHV-7 in the pathophysiology of ME/CFS.
The cases with HHV-7-specific sequence in DNA isolated from cell free blood plasma were defined as active HHV-7 infection cases. The presence of HHV-7-specific antibodies was not examined due to the lack of commercial test systems for IgM class antibody detection.