Herpes simplex encephalitis (HSE)

While encephalitis is rare in the United States, when it does occur it is usually caused by the herpes simplex virus.1

Symptoms typical of herpes simplex encephalitis (HSE) that are less likely to occur in other types of encephalitis include speech problems, a reduced sense of smell, and partial seizures. Fever and headache occur as in other types of encephalitis. HSE usually can be diagnosed through analysis of spinal fluid obtained through a lumbar puncture (spinal tap).

In cases of HSE, early treatment (before the person becomes unconscious) with an antiviral medicine called acyclovir greatly increases the possibility of survival and recovery.1

When HSE is not treated, it has a death rate of 70% to 80%.2 Of people who survive the disease, many have permanent neurological problems, including seizures, memory loss, and dementia.


  1. Roos KL (2003). Encephalitis. In RW Evans, ed., Saunders Manual of Neurologic Practice, pp. 711–713. Philadelphia: Saunders.
  2. Jubelt B (2005). Viral infections. In LP Rowland, ed., Merritt's Neurology, 11th ed., chap. 24, pp. 175–210. Philadelphia: Lippincott Williams and Wilkins.

Last Updated: August 5, 2008

related physicians

related services

Bon Secours International| Sisters of Bon Secours USA| Bon Secours Health System

This information does not replace the advice of a doctor. Healthwise disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. Privacy Policy. How this information was developed to help you make better health decisions.

© 1995-2010 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.