Encyclopedia of Health and Medicine

D–E
diphtheria An illness that results from INFECTION
with the bacterium Corynebacterium diphtheriae.
Routine childhood IMMUNIZATION has made diphtheria
rare in the United States, though the infection
can occur in people who do not receive a
booster VACCINE every 10 years and is common in
other parts of the world.
Infection may involve the NOSE and THROAT (respiratory
diphtheria) or the SKIN (cutaneous diphtheria).
C. diphtheriae BACTERIA that infect the
throat produce a toxin that causes a thick layer of
cells and mucus to accumulate in the throat,
forming a membrane that impairs BREATHING. Respiratory
diphtheria is life threatening and requires
urgent administration of diphtheria ANTITOXIN,
which counters the toxin the C. diphtheriae bacteria
produce, in combination with ANTIBIOTIC MED-
ICATIONS to kill the C. diphtheriae bacteria (typically
erythromycin or penicillin G). Diphtheria that
occurs in the United States is most often cutaneous.
Cutaneous diphtheria causes painful, red
sores on the skin. Antibiotic therapy is often adequate
to treat the infection, though sometimes
doctors also administer diphtheria antitoxin.
The INCUBATION PERIOD for either type of diphtheria
is two to five days after exposure. The infection
is contagious for up to two weeks after
symptoms emerge. The course of uncomplicated
illness is four to six weeks. Respiratory diphtheria
(especially when untreated) may result in complications
that include MYOCARDITIS (INFLAMMATION
and infection of the HEART MUSCLE), NEURITIS, RESPI-
RATORY FAILURE, and death. Childhood immunization
with booster vaccines every 10 years is the
most effective means of prevention. Some people
are carriers of C. diphtheriae bacteria, which
requires human hosts for survival. Carriers have
the infection present in their bodies but do not
become ill, though they can pass the infection to
others. ANTIBIOTIC PROPHYLAXIS prevents infection in
people who are exposed to C. diphtheriae.
See also CHILDHOOD DISEASES; PREVENTIVE HEALTH
CARE AND IMMUNIZATION.
encephalitis INFLAMMATION and INFECTION of the
BRAIN. Encephalitis usually results from infection
with a VIRUS and is potentially life threatening.
Infection can enter the brain via pathogens that
are small enough to pass across the BLOOD–BRAIN
BARRIER or that are able to follow neural pathways
(the routes of nerves) into the brain. The most
common cause of encephalitis is infection with an
arbovirus transmitted through the bite of a mosquito
or tick. Other viruses that typically cause
common infections may affect the brain to cause
encephalitis, and encephalitis may develop as a
complication of viral infection (and less commonly
bacterial infection) elsewhere in the body. TOXO-
PLASMOSIS, a parasitic infection, may also cause
encephalitis.
VIRUSES THAT CAN CAUSE ENCEPHALITIS
CYTOMEGALOVIRUS (CMV)
California VIRUS
eastern equine virus
EPSTEIN-BARR VIRUS
HERPES SIMPLEX virus (HSV)
LaCrosse virus
MUMPS virus
Powassan virus
RUBELLA virus
rubeola (MEASLES) virus
St. Louis virus
varicella zoster viruses
West Nile virus
western equine virus
Symptoms and Diagnostic Path
The symptoms of encephalitis differ somewhat in
children and in adults. Children often become
lethargic, confused, irritable, and sensitive to light;
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