if you have HHV-6, the normal strain it is no worry. it can be "reactivated" under stress, like shingles. but i wouldn't put weight on it.

HHV-6, or human herpesvirus 6, is a subtle but insidious virus that can invade the central nervous system and cause low-grade inflammation that persists for years. Once thought to be a benign virus that caused only roseola in infants, HHV-6 is now known to cause profound immunosuppression and serious disease. Much of the early research was inconclusive due to a poor understanding of the virus and the poor quality of tests available to detect active vs. latent disease. Recent studies using more sensitive techniques have found HHV-6 to be associated with the following conditions:

* Chronic Fatigue Syndrome
* Multiple Sclerosis
* Cancer
* Seizures & Febrile Illness
* Epilepsy
* Interstitial Pneumonitis
* AIDS & HIV Encephalopathy (PML)
* Immunosuppression
* Complications in Transplant Patients
* Non-EBV Mononucleosis
* Drug Hypersensitivity Syndrome

While it is generally known that this virus causes roseola and occasional seizures and encephalitis in infants, most physicians are not aware of the new disease associations or the fact that the immunosuppression caused by HHV-6 can predispose other disease states such as AIDS to progress more rapidly. HHV-6 viral infection results in increased levels of inflammatory cytokines such as IL-1 and TNF α, and a steep reduction in IFN γ, which is necessary to fend off cancer, intracellular pathogens, viruses and mycobacteria.

HHV-6, a beta herpesvirus in the same family as cytomegalovirus, was discovered in 1986 in AIDS patients with cancer and lymphoproliferative disorders. It infects close to 100% of children by the age of two, causing mild flu-like symptoms in most, but serious rash, high fever, encephalitis and seizures in a significant number of children. A surprisingly high percentage of pediatric emergency room visits are due to primary HHV-6 infections. These primary infections are far from benign: 13% of infants with acute HHV-6 infections develop seizures, sometimes leading to encephalitis. The virus then persists in the CNS. In most cases, the virus goes into latency; however, in patients with impaired immune function, the virus persists in its active state at low levels for years .

There are two distinct variants of HHV-6. Variant A or HHV-6A, is the predominant strain found in MS, CFS and AIDS patients. HHV-6B is the strain that causes roseola, febrile illnesses encephalitis in infants, and reactivates in transplant patients leading to progression of CMV disease or rejection of the organ.

Strong association with CFS and MS

Research proving the association of HHV-6 with diseases such as Multiple Sclerosis (MS) and Chronic Fatigue Syndrome (CFS) has been sadly handicapped by several negative studies that used incorrect testing methodology. Because latent infection is so widespread, only tests that can differentiate between the active and latent infection are meaningful . Since up to 97% of us carry latent infection, this distinction is critical.

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 either MS or CFS, contradicting many positive studies and creating confusion. When the best testing method (a test that measures "early antigen" (EA) or active infection only) has been used, there have been dramatic disease associations suggesting an important role for HHV-6 in these conditions:

MS & HHV-6

* Researchers at the NIH found that 73% of MS patients with relapsing remitting disease were positive for HHV-6A IgM antibodies to EA, vs. 18% of normal controls. (Soldan et al, Nature, 1997)

* Ablashi et al found 70% of MS patients had HHV-6 IgM antibodies against the early antigen vs. 15% of healthy donors. (J Clin Virol, 2000)

CFS & HHV-6

* Ablashi et al found 54% of CFS patients were positive for HHV-6 IgM early antigen antibodies compared to 8% of healthy donors. (J Clin Virol, 2000)

* Patnaik and Komaroff found 77% of CFS patients positive for HHV-6 IgG early antigen antibodies vs. 12% of controls. (J Inf Dis, 1995)

HHV-6 & Cancer

HHV-6 induced immunosuppression puts patients with chronic active infections at risk for cancer. Both beta herpesvirues (cytomegalovirus, HHV-6 and HHV-7) and gamma herpesviruses (Epstein Barr Virus and HHV-8) have been recently identified as risk factors for many types of cancer, in particular lymphoma and Kaposi's Sarcoma. HHV-6 is one of the few viruses (other than HIV) that can directly infect CD4 + T-cells. HHV-6 can also infect natural killer cells, which are critical for protection against cancer and viral infection. The following cancers have been associated with increased levels of HHV-6 antibodies or HHV-6 DNA: oral cancer, Hodgkin's and non-Hodgkin's lymphoma, acute lymphoblastic leukemia, multiple myeloma and myeloproliferative disorder syndrome.

In sum, HHV-6 is quietly damaging the health of a great number of patients across a wide range of illnesses.

http://www.hhv-6foundation.org