Encyclopedia of Health and Medicine

Epstein-Barr virus 323
older children may complain of severe HEADACHE.
Adults often exhibit changes in mental alertness,
cognitive ability, and emotional stability and may
have severe headache. Both children and adults
may have seizures, FEVER, NAUSEA, and VOMITING.
Diminished awareness or loss of consciousness
that accompanies or follows
other symptoms of encephalitis is an
indication of serious INFECTION that
requires urgent medical attention.
The diagnostic path includes LUMBAR PUNCTURE to
determine the presence of pathogens or white
BLOOD cells, or excessive fluid or increased pressure
in the spinal column, any of which may indicate
infection. Blood tests may show the presence of
certain viruses. Diagnostic procedures such as electroencephalogram
(EEG) and COMPUTED TOMOGRA-
PHY (CT) SCAN or MAGNETIC RESONANCE IMAGING (MRI)
can show abnormalities of brain function and
structure that are characteristic of encephalitis.
Treatment Options and Outlook
Mild viral encephalitis generally runs its course
within five to seven days and does not require
treatment beyond ANALGESIC MEDICATIONS such as
acetaminophen to relieve fever and headache.
ANTIVIRAL MEDICATIONS can reduce the severity of
symptoms and length of illness for some forms of
viral encephalitis, notably those resulting from
viruses in the herpes family, though have no effect
against encephalitis resulting from arboviruses.
CORTICOSTEROID MEDICATIONS to suppress the inflammatory
response can reduce intracranial swelling
and pressure that commonly accompanies
encephalitis. Bacterial encephalitis, which is much
less common than viral encephalitis and usually a
secondary infection, requires treatment with
antibiotic medications. Antibiotics are not effective
against viral infections.
Recovery depends on the severity of symptoms
and the causative PATHOGEN. Though viral
encephalitis is generally more mild than bacterial
encephalitis, it can be fatal, particularly in infants,
the very elderly, and people who are IMMUNOCOM-
PROMISED. People who have mild encephalitis
recover completely and without residual complications.
More severe illness may result in permanent
brain damage and corresponding cognitive
dysfunction, memory impairment, LEARNING DISOR-
DERS, PARALYSIS, SEIZURE DISORDERS, or speech disorders.
Risk Factors and Preventive Measures
The risk for viral encephalitis is greatest during
times of the year when mosquito and tick activity
is highest, typically May through October in most
parts of the United States. Other risks include living
in close contact, such as in dormitories and
institutions, and infection elsewhere in the body
that migrates to the brain. Prevention efforts
include public health measures to control mosquito
populations and individual efforts to minimize
exposure to mosquitoes and ticks.
See also COGNITIVE FUNCTION AND DYSFUNCTION;
MEMORY AND MEMORY IMPAIRMENT; MENINGITIS.
Epstein-Barr virus A member of the herpesvirus
family best known for causing the illness infectious
mononucleosis. INFECTION with the Epstein-
Barr VIRUS, also called human herpesvirus-4
(HHV-4), causes other disease as well and was the
first virus researchers linked with cancer (notably
Burkitt’s lymphoma). Epstein-Barr virus is ubiquitous;
it infects more than 90 percent of Americans
by age 25.
As is characteristic of herpesvirus infections,
Epstein-Barr virus causes first an acute illness
(infectious mononucleosis), then retreats into a
state of dormancy and remains in the body as a
latent infection that does not cause illness or
symptoms. B-cell lymphocytes, white BLOOD cells
key to ANTIBODY-MEDIATED IMMUNITY, harbor the
latent Epstein-Barr virus. Though the virus does
not change the ability of its host B-cell lymphocytes
to function within the IMMUNE RESPONSE, it
does alter their DNA such that they become
immortalized—they lose their genetic encoding for
APOPTOSIS, the natural process for cell death.
Only a small percentage of B-cell lymphocytes
contain the virus, so for the most part immune
function continues as normal. A healthy IMMUNE
SYSTEM maintains a balance between B-cell lymphocytes
and T-cell lymphocytes (white blood cells
key to CELL-MEDIATED IMMUNITY) that prevents B-