Viral Encephalitis

Encephalitis is an inflammation of the brain caused, most often, by a viral infection. The specific viruses that cause encephalitis vary. Exposure to viruses that cause encephalitis occur mostly through insect bites. The virus enters through the blood stream and spreads to the brain, causing inflammation of the nerve cells (encephalitis) and/or surrounding membranes (meningitis). Encephalitis is different than meningitis, but these two brain infections often occur together. Although the vast majority of individuals with encephalitis recover after a long period of time, inflammation may cause irreparable damage to the brain, bleeding within the brain, and even death. An estimated 10,000 to 20,000 cases of encephalitis are reported annually in the United States.

Signs and Symptoms


Arboviruses, or viruses carried by insects, are among the most common causes of viral encephalitis. Some of the major arboviruses include: Other viruses that commonly cause viral encephalitis include: Less common causes include: Not all cases of encephalitis are caused by viruses. Some nonviral causes of encephalitis include:

Risk Factors

The following factors may increase an individual's risk for becoming infected with viral encephalitis:


Encephalitis is a serious condition, so diagnosis and initial treatment usually take place in a hospital setting. After performing a physical exam, a physician may take the following steps to diagnose the condition:

Preventive Care

The most effective way for an individual to prevent encephalitis is to avoid contracting viruses that lead to encephalitis:

Treatment Approach

Because encephalitis is a serious condition that can cause severe complications, treatment usually occurs in the hospital and sometimes requires intensive care. Generally, there are no specific medications to treat the viruses causing encephalitis. HSV1, VZV, and EBV are exceptions to this rule, however, as acyclovir is an excellent treatment. Often, people with symptoms of encephalitis are treated with this medication until the virus causing the condition is identified. Behavioral techniques, such as those used to treat individuals with traumatic brain injury, have been recently explored in the treatment of individuals recovering from the condition. Although complementary and alternative therapies have not been extensively studied for the treatment of encephalitis, some studies indicate that scalp acupuncture, combined with proper medication, may aid in the healing process. Careful observation and supportive care, including rest, proper nutrition, and fluids are a mainstay of treatment for encephalitis and allow the body to fight the infection.


Medications used to treat viral encephalitis include:

Nutrition and Dietary Supplements

Although nutrition and dietary supplements have not been scientifically evaluated for use in treating encephalitis in humans, some studies suggest that melatonin may protect animals from serious complications associated with the condition and even increase their survival rates. In one study of mice that had been infected with Venezuelan equine encephalitis virus, melatonin supplements significantly reduced the presence of viruses in the blood and decreased the rate of death by more than 80%. More studies are needed, however, to determine whether similar treatment may offer the same protection to humans with viral encephalitis.


Astragalus (Astragalus membranaceus)
Animal studies suggest that Astragalus (Astragalus membranaceus), an herb used in Asia to improve weakness and to enhance immune function, may also protect humans from contracting viral encephalitis. In one study, mice that were given astragalus extracts before being infected with Japanese encephalitis virus, had a 60% to 80% chance of survival. Mice that did not receive astragalus extracts before being infected with the virus only had a 10% chance of survival. More studies are needed, however, to determine whether similar treatment may offer the same protection to humans with viral encephalitis.
Professional herbalists may also use a combination of herbs to relieve the symptoms associated with viral encephalitis, such as cognitive impairment, visual and speech disturbances, and difficulty performing routine functions. This herbal mixture includes:


A study of a small number of individuals with complications associated with encephalitis suggests that acupuncture delivered to the scalp may lessen the severity of such complications and reduce the symptoms associated with the condition. Some researchers theorize that scalp acupuncture is effective for individuals with encephalitis because all meridians converge at the head, and the method can stimulate and regulate qi throughout the entire body. More research is necessary, however, to conclusively determine whether scalp acupuncture is safe and effective for individuals with encephalitis.

Massage and Physical Therapy

Behavioral and Physical Training
Recently, behavioral and physical training techniques have been explored in the treatment of individuals recovering from encephalitis. In one case, a woman experiencing poor short-term memory and decreased muscle coordination as a result of viral encephalitis began to improve significantly after participating in a behavioral rehabilitation training program. As a result of the program, she gained a high level of independence and was able to return home from the hospital with only minimal assistance by a caregiver. More studies are needed to determine whether behavioral training is safe and effective for other individuals recovering from encephalitis.

Other Considerations

The most common cause of encephalitis in newborns is vaginal delivery from a mother who is infected with herpes simplex virus 2 (HSV 2). This infection in newborns is often severe and fatal. For this reason, cesarean section may be advised for pregnant women with a history of HSV 2, even if there is no sign of an active infection.

Prognosis and Complications
Full recovery from encephalitis can take weeks or months, during which time many individuals experience complications ranging from fatigue and difficulty concentrating to tremors and personality changes. The most severe complications associated with encephalitis result from the destruction of nerve cells in the brain that do not regenerate. The severity of complications depends on the condition of the immune system (whether it is healthy or weak) and the infection causing the encephalitis. For example, 80% of those infected with Eastern equine encephalitis, St. Louis encephalitis, and Japanese encephalitis, have permanent neurologic impairments (such as memory, speech, vision, hearing, muscle control, and sensation) and a very low survival rate, while those infected with EBV or Venezuelan equine encephalitis rarely experience any serious complications. The long-term outlook for those with HSV encephalitis depends primarily on how quickly the condition is treated.

Between 80% and 95% of individuals infected with viral encephalitis will survive the condition, but 20% will experience debilitating side effects or complications, such as memory loss or severe personality changes. The survival rate for those with HSV encephalitis increases dramatically from 30% to 70% when the condition is detected early and treated with antiviral medications.


Acyclovir. NMIHI. Accessed at

Adams RD, Victor M, Ropper AH. Principles of Neurology. 6th ed. New York, NY: McGraw-Hill; 1997:749-755.

Arribas JR, Storch GA, Clifford DB, Tselis AC. Cytomegalovirus encephalitis. Ann Intern Med. 1996;125(7):577-587.

Bale JF Jr. Viral encephalitis. Med Clin North Am. 1993;77(1):25-42.

Ben-Nathan D, Maestroni GJ, Lustig S, Conti A. Protective effects of melatonin in mice infected with encephalitis viruses. Arch Virol 1995;140(2):223-230.

Bonilla E, Valero-Fuenmayor N, Pons H, Chacin-Bonilla L. Melatonin protects mice infected with Venezuelan equine encephalomyelitis virus. Cell Mol Life Sci 1997;53(5):430-434.

Clifton ER. Herpes simplex encephalitis: an overview. J Miss State Med Assoc. 1991;32(12):437-440.

Encephalitis. Symptoms and causes. MFMER. Accessed at on February 11, 2018.

Evansa RW: Diagnostic Testing in Neurology. Philadelphia, Pa: W.B. Saunders Company; 1999:187-188.

Fauci AS, Braunwald E, Isselbacher KJ, et al, eds. Harrison's Principles of Internal Medicine. 14th ed. Vol 1. New York, NY: McGraw-Hill; 1998:1136-1139, 2442-2445.

Feign RD, Cherry JD. Textbook of Pediatric Infectious Diseases. 3rd ed. Vol 1. Philadelphia, Pa: W.B. Saunders Company; 1992:445-452.

Fluconazole. NMIHI. Accessed at

Gorbach SL, Bartlett JG, Blacklow NR: Infectious Diseases. 2nd ed. Philadelphia, Pa: W.B. Saunders Company; 1998:1408-1414.

Gresikova M, Kaluzova M. Biology of tick-borne encephalitis virus. Acta Virol. 1997;41(2):115-124.

Irani MT, Singh AR, Udwadia AD, Merchant RH. Neonatal herpes simplex virus-2 encephalitis. Indian Pediatr. 1995;32(4):476-480.

Johnson RT. Acute encephalitis. Clin Infect Dis. 1996;23(2):219-224.

Kajimura K, Takagi Y, Ueba N, et al. Protective effects of Astragali radix by intraperitoneal injection against Japanese encephalitis virus infection in mice. Biol Pharm Bull. 1996;19(6):855-859.

Katzmann S, Mix C. Improving functional independence in a patient with encephalitis through behavior modification shaping techniques. Am J Occup Ther. 1994;48(3):259-262.

Levitz RE. Herpes simplex encephalitis: a review. Heart Lung. 1998;27(3):209-212.

Liang D. Treatment of the sequelae of viral encephalitis by needling Sishencong (Extra). J Chinese Med. 1996;50:26.

Luft BJ, Remington JS. Toxoplasmic encephalitis in AIDS. Clin Infect Dis. 1992;15(2):211-222.

Mrak RE, Young L. Rabies encephalitis in humans: pathology, pathogenesis, and pathophysiology. J Neuropathol Exp Neurol. 1994;53(1):1-10.

O'Meara M, Ouvrier R. Viral encephalitis in children. Curr Opin Pediatr. 1996;8(1):11-15.

Roos KL. Encephalitis. Neurol Clin. 1999;17(4):813-833.

Rosen P, et al. Emergency Medicine: Concepts and Clinical Practice. 4th ed. Vol 3. St. Louis, Mo: Mosby; 1998:2198-2209.

Rubeiz H, Roos RP. Viral meningitis and encephalitis. Semin Neurol. 1992;12(3):165-177.

Rust RS, Thompson WH, Matthews CG, Beaty BJ, Chun RW. La Crosse and other forms of California encephalitis. J Child Neurol. 1999;14(1):1-14.

Samuels MA, Feske S. Office Practice of Neurology. New York, NY: Churchill Livingstone; 1996:401-408.

Skoldenberg B. Herpes simplex encephalitis. Scand J Infect Dis Suppl. 1996;100:8-13.

Toltzis P. Viral encephalitis. Adv Pediatr Infect Dis. 1991;6:111-136.

Whitley RJ, Kimberlin DW. Viral encephalitis. Pediatr Rev. 1999;20(6):192-198.

What is encephalitis? MedicalNews. Accessed at

Viral Encephalitis signs and symptoms. NMIHI. Accessed at

Zupanc ML, Handler EG, Levine RL, et al. Rasmussen encephalitis: epilepsia partialis continua secondary to chronic encephalitis. Pediatr Neurol. 1990;6(6):397-401.