HHV-6 is an infection that can persist in the brain tissue long after the primary infection and after evidence of the virus has long disappeared from the plasma in the circulating blood. Therefore, direct evidence of chronic infection is not easily attainable by standard laboratory tests, even though it has long been suspected as playing a role in chronic fatigue syndrome (CFS), in conjunction with Epstein Barr Virus (EBV) the virus that causes mononucleosis.
Ironically, 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. (See Testing for HHV-6)
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. He is now planning a placebo-controlled trial.(See Stanford press release)
Most physicians are reluctant to use a strong antiviral without certainty that the virus is active. Antibody levels can remain elevated for years after the primary infection and in some cases, merely indicate a healthy response to a past infection. Montoya reasoned, however that since 97% of us have had our primary infection with HHV-6 by the age of two, highly elevated antibody levels in an adult could mean active disease. His results so far suggest that his theory may be correct. Antibody levels to both HHV-6 and EBV dropped with treatment. (Montoya 2006). His initiative is invaluable because treatment results will provide clarity where diagnostic studies have failed to provide an answer.
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 don’t 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.
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This is one area being explored as a possible cause of adverse reaction and death in the girls injured by the HPV vaccines. Chronic Fatigue Syndrome (CFS) is common amongst the adversely affected.