Herpes Simplex Encephalitis

Herpetic infections have been well-documented, as far back as ancient Greek literature. Herpes viruses are large double-stranded DNA viruses. Eight types of herpes viruses affect humans (human herpes virus—HHV). Symptoms of central nervous system infection include fever, headache, seizures, focal neurological signs, and impaired consciousness.

Herpes simplex encephalitis is an acute or subacute illness associated with focal or global cerebral dysfunction caused by herpes simplex viruses belonging to either type 1 (HSV-1) or type 2 (HSV-2). Most herpes simplex encephalitis is caused by HSV-1, with HSV-2 constituting less than 10% of infections. Almost all herpes encephalitis beyond the neonatal period is caused by herpes simplex type 1 (HSV-1), the most common cause of fatal encephalitis, occurring in a sporadic and non-seasonal pattern across the globe. Herpes encephalitis in neonates could be due to HSV-1 or HSV-2, though the latter is more common. HSV-2 can also cause encephalitis in immunocompromised patients.

HSV-1 in adults is associated with significant morbidity and mortality despite treatment with antiviral therapy. Herpes simplex encephalitis has a nonspecific and insidious onset in children and can be devastating, irrespective of treatment. Herpes simplex encephalitisis a rare condition, but if left untreated, it can result in a mortality rate of up to 70%, and only a minority of individuals recover fully without residual deficits. Neonatal encephalitis caused by HSV-2 involves the brain in a more global distribution, resulting in a greater incidence of neurologic sequelae.