Human Herpesviruses 6A and 6B in Brain Diseases: Association versus Causation

Human herpesvirus 6A (HHV-6A) and human herpesvirus 6B (HHV-6B), collectively termed HHV-6A/B, are neurotropic viruses that permanently infect most humans from an early age. Although most people infected with these viruses appear to suffer no ill effects, the viruses are a well-established cause of encephalitis in immunocompromised patients. In this review, we summarize the evidence that the viruses may also be one trigger for febrile seizures (including febrile status epilepticus) in immunocompetent infants and children, mesial temporal lobe epilepsy, multiple sclerosis (MS), and, possibly, Alzheimer's disease. We propose criteria for linking ubiquitous infectious agents capable of producing lifelong infection to any neurologic disease, and then we examine to what extent these criteria have been met for these viruses and these diseases.

Automated summary

This review examines the evidence that Human herpesvirus 6A (HHV-6A) and human herpesvirus 6B (HHV-6B) may trigger neurological diseases in humans, including encephalitis in immunocompromised patients and febrile seizures in infants and children. It also discusses the criteria for linking infectious agents to neurologic diseases and evaluates the extent to which these criteria have been met for HHV-6A/B and various neurological conditions.