Introduction to HHV-6

Introduction to HHV-6

Source: HHV-6 foundation

Human Herpesvirus 6 (HHV-6) is a set of two closely related herpes viruses known as HHV-6A and HHV-6B that infect nearly all human beings, typically before the age of two. The acquisition of HHV-6 in infancy is often symptomatic, resulting in childhood fever, diarrhea, and exanthem subitum rash (commonly known as roseola). Although rare, this initial infection can also cause febrile seizures, encephalitis or intractable seizures.

Like the other herpesviruses—Epstein Barr virus, varicella zoster virus, etc—HHV-6 establishes life-long latency and can become reactivated later in life. This reactivation has been associated with many clinical manifestations that can be seen in the “Associated Conditions” section of this site. Reactivation can occur in locations throughout the body, including the brain, lungs, heart, kidney and gastrointestinal tract. In some cases, HHV-6 reactivation in the brain tissue can cause cognitive dysfunction, permanent disability and death.

A growing number of studies also suggest that HHV-6 may play a role in a subset of patients with chronic neurological conditions such as multiple sclerosis, mesial temporal lobe epilepsy, status epilepticus and chronic fatigue syndrome. There is an urgent need for more studies that can prove or disprove the important disease associations that have been suggested.

Since its discovery in 1986, HHV-6 has been associated with a wide array of clinical conditions—many of which are listed in the menu at right. While the relationship between HHV-6 infection and some of these diseases are well established, the role of HHV-6 in many other conditions remains unclear. In addition to causing “acute” disease such as encephalitis, HHV-6 can also persist as a chronic infection, nearly undetectable by most current diagnostic tests. This subacute form of HHV-6 is likely to contribute to the pathology of many diseases associated with HHV-6. There is an urgent need for more sensitive diagnostic assays and studies that can prove or disprove the important disease associations that have been suggested.

Established Disease Assocations

Transplant Complications

  • Bone marrow supression
  • Colitis/diarrhea
  • Delirium/CNS Dysfunction
  • Encephalitis/Amnesia
  • GVHD
  • Hemophagocytic syndrome
  • Hepatitis /Liver failure
  • Pneumonitis
  • Transplant Reactivation Overview


  • Encephalitis / Meningitis Overview
  • Encephalitis in the Immunocompromised
  • Encephalitis in the Immunocompetent
  • Rhomboencephalitis
  • Limbic Encephalitis
  • Encephalomyelitis
  • Amnesia

Rash & Roseola


  • Febrile Seizures
  • Status Epilepticus

Cognitive Dysfunction

  • Delirium
  • Amnesia

Hypersensitivity (DIHS/DRESS)

  • Drug Induced Hypersensitivity Syndrome (DIHS)
  • Drug Reaction with Eosinophilia & Systemic Symptoms (DRESS)
  • Stevens-Johnson Syndrome (SJS)

Immune Suppression

  • Bone Marrow Suppression


Possible Disease Associations

Multiple Sclerosis

Chronic Fatigue Syndrome


  • Mesial/Temporal Lobe Epilepsy
  • Status Epilepticus


Endocrine Disorders

Heart Disease

  • Myocarditis
  • Left Ventricle Disfunction
  • Arteriopathies

Hemophagocytic Conditions

  • Hemophagocytic Syndrome/ Histiocytosis

HIV/AIDS Progression

Liver Disease

  • Hepatitis
  • HIV/AIDS Progression

Lung Disease

  • Organizing Pneumonia
  • Pneumonitis


  • Hodgkin’s Lymphoma
  • Gliomas
  • Cervical Cancer

Kidney Disease

Autoimmune Disease

Other Associations

  • Hypogammablogulinemia
  • Optic Neuritis
  • Microangiopathy
  • Mononucleosis
  • Uveitis