Human herpesvirus 6

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Human herpesvirus 6 (HHV-6) is a set of two closely related herpesviruses, HHV6-A and HHV6-B. Infection is extremely common and usually occurs at an early age. 64-83% of infants are infected by age 13 months.[1] HHV-6 has an affinity for leukocytes and nervous tissue, especially the olfactory bulb tissues[2], from which it is thought to disseminate to other parts of the brain. After infection the virus remains latent but can reactivate asymptomatically even in healthy individuals.

HHV-6 has been found to activate Epstein-Barr virus from latency. Conversely, the presence of EBV renders B cells more susceptible to HHV-6 infection.[3]

In human disease[edit | edit source]

HHV-6 has been implicated as a contributing factor to a number of neurological diseases including multiple sclerosis[4], chronic fatigue syndrome[5] and epilepsy, as well as fibromyalgia and AIDS.

Multiple sclerosis[edit | edit source]

HHV-6 has been found in the oligodendrocytes of plaques in MS patients but not in healthy tissue.[6]

Antivirals may have some therapeutic benefit. A randomized, placebo-controlled double-blind study found that acyclovir reduced the exacerbation rate in relapsing-remitting MS patients.[7]. Valacyclovir reduced new lesions in patients with high disease activity.[8]

Cancer[edit | edit source]

Like Epstein-Barr virus, HHV-6 is associated with lymphomas and carcinomas.[9]

Chronic fatigue syndrome[edit | edit source]

One study found a higher prevalence of past HHV-6 infection in chronic fatigue syndrome patients but with a low viral load that did not suggest reactivation.[10] Several studies have found that active infection is more common in CFS patients than healthy controls.[11]

Antivirals[edit | edit source]

There have been no controlled trials of antivirals for HHV-6. Those used clinically are the drugs used for human cytomegalovirus: ganciclovir, valganciclovir, and to a lesser extent acyclovir.

Notable studies[edit | edit source]

Learn more[edit | edit source]

See also[edit | edit source]

References[edit | edit source]

  4. Pietiläinen-Nicklén J, Virtanen JO, Uotila L, Salonen O, Färkkilä M, Koskiniemi M. (2014). HHV-6-positivity in diseases with demyelination. Journal of Clinical Virology, 61 (2):216-9. doi: 10.1016/j.jcv.2014.07.006. Epub 2014 Jul 21. Rerieved from
  12. Aoki, R; Kobayashi, N; Suzuki, G; Kuratsune, H; Shimada, K; Oka, N; Takahashi, M; Yamadera, W; Iwashita, M; Tokuno, S; Nibuya, M; Tanichi, M; Mukai, Y; Mitani, K; Kondo, K; Ito, H; Nakayama, K (2016), "Human herpesvirus 6 and 7 are biomarkers for fatigue, which distinguish between physiological fatigue and pathological fatigue", Biochemical and Biophysical Research Communications, 478 (1): 424-30, doi:10.1016/j.bbrc.2016.07.010, PMID 27396623 

chronic fatigue syndrome (CFS) - A controversial term, invented by the U.S. Centers for Disease Control, that generally refers to a collection of symptoms as “fatigue”. There have been multiple attempts to come up with a set of diagnostic criteria to define this term, but few of those diagnostic criteria are currently in use. Previous attempts to define this term include the Fukuda criteria and the Oxford criteria. Some view the term as a useful diagnostic category for people with long-term fatigue of unexplained origin. Others view the term as a derogatory term borne out of animus towards patients. Some view the term as a synonym of myalgic encephalomyelitis, while others view myalgic encephalomyelitis as a distinct disease.

The information provided at this site is not intended to diagnose or treat any illness.
From MEpedia, a crowd-sourced encyclopedia of ME and CFS science and history.