The Association Between Herpes Simplex Viruses (Type One and Two) and Autism Spectrum Disorders

Over the last twenty years, there has been an impressive rise in Autism spectrum disorders with current prevalence estimates being about one over one hundred children.

Herpes simplex virus encephalitis is the leading cause of sporadic, nonepidemic encephalitis in children and adults in the United States. It is an acute necrotizing infection generally involving the frontal and/or temporal cortex and the limbic system and, beyond the neonatal period, is almost always caused by Herpes simplex virus type on.

The etiology of autism is unknown; data suggest that autism results from multiple etiologies with both genetic and environmental contributions. One proposed etiology for autism is viral infection very early in development. The mechanism, by which viral infection may lead to autism, be it through direct infection of the central nervous system, through infection elsewhere in the body acting as a trigger for disease in the central nervous system, through alteration of the immune response of the mother or offspring, or through a combination of these, is not yet known.

Many encephalitic patients had temporal lobe involvement. Autism results from neuropathology relating to the temporal lobes. They speculate the differences in the extent and neuropathologies of the temporal lobes contribute to the heterogeneity of autism. Also, herpes viruses can induce a variety of proinflammatory cytokines during infections, along with elevated interferon in the brain during Herpes simplex virus encephalitis.