HHV-6 is an infection that can persist in your brain tissue long after the initial infection and long after the evidence has disappeared from your blood. So having the direct evidence or proof of chronic infection is not easy to get from standard blood testing. After years of being sick with CFS, it wasn’t until I went to the Fibro & Fatigue Centers that all of these “chronic infections” (HHV-6 was one of them) were found. But even though gathering this evidence has not been simple, it has been suspected for years that these chronic infections (HHV-6, EBV) have played a huge role in CFS.
According to the HHV-6 Foundation:
…one of the best tests for active infection may turn out to be not the new PCR tests, but rather the widely available and relatively inexpensive HHV-6 IgG antibody IFA test, using a high cutoff. While an HHV-6 IgG titer of say 1:640 might be perfectly normal for a 4 year old, or a teenager just over a bout of mononucleosis, it is not common in a 45 year old, and could be a sign of active infection. (IgM titers are rarely positive except after the primary infection. One study of CFS patients found that elevated antibody titers do correlate with active infection by culture.
Ultimately, it may be impossible to find direct evidence of the virus, and the only way to prove if an association exists is to treat for virus to see if the patients get better. This is exactly what infectious disease specialist Jose Montoya, MD from Stanford University did with 12 patients he treated for long standing fatigue and elevated antibody titers to HHV-6 and EBV. He established a high cutoff and then treated these patients with a strong antiviral; an astounding 75% improved dramatically. Some of these patients had been sick for over 10 years.
Many physicians do not want to use these tests because they feel uncertain that the virus is active because the antibody levels can remain elevated for years after infection. Dr. Montoya rationalizes that because 97% of the population has been infected with the HHV-6 virus by the time they are two years of age that highly elevated levels of the virus in an adult can mean active disease. Dr. Montoya’s results have shown that his theory may be correct, since the antibody levels of HHV-6 and EBV levels dropped with treatment.
Also according to the HHV-6 Foundation:
Efforts to establish an association between HHV-6 and CFS have been complicated by the fact that several studies have been published using tests that dont differentiate between active and latent infection. These studies showed no association between HHV-6 and or CFS, contradicting the positive studies and creating confusion. When a measures were used that can detect active infection such as IgG early antigen antibodies (which are present only during active infection), there have been dramatic disease associations suggesting an important role for HHV-6 in these conditions. Only longitudinal studies using correct testing methodology will provide conclusive answers.