Encyclopedia of Health and Medicine

332 Infectious Diseases
symptoms develop as organs fail. The only treatment
for viral hemorrhagic fevers is supportive;
the illnesses are usually fatal. Outbreaks of viral
hemorrhagic fevers occur periodically. Global
efforts are under way to find medical treatments
that can halt the course of disease as well as to
contain rodent, mosquito, and tick populations.
See also COMMUNITY SANITATION.
herpes simplex INFECTION with the herpes simplex
VIRUS 1 (HSV-1) or HSV-2. HSV-1 primarily
causes cold sores on the lips and in the MOUTH,
transmitted through saliva. HSV-2 primarily
causes GENITAL HERPES, a sexually transmitted disease
(STD) that causes ulcerative sores on the genitals.
However, either form of the virus can cause
infection anywhere in the body. HSV-1 and HSV-
2, like other herpes viruses, are highly contagious
through contact with the sores and may also
spread from one person to another even when no
sores are present. Herpes simplex infection is lifelong,
though symptoms characteristically wax and
wane. About 90 percent of Americans have HSV-1
and about 30 percent have HSV-2.
The typical course of an outbreak begins with
itching or tingling, called the prodrome, which
gives way to the eruption of a BLISTER within 48
hours. Cold sores typically form as single blisters
though may occur as multiple blisters in several
locations; genital herpes sores tend to erupt in
clusters. After two or three days the blisters rupture
and form crusted sores that subsequently
heal. The cycle from prodrome to HEALING lasts
about 10 days. Because the course of illness is so
characteristic, the doctor can usually make the
diagnosis on the appearance of the sores. Laboratory
culture of the fluid within a blister or sore
can provide a definitive diagnosis.
After an outbreak of symptoms the virus
retreats to the local NERVE roots where it remains
dormant until the next outbreak. Researchers are
not certain what factors initiate outbreaks though
stress and exposure to sunlight appear to play key
roles. Doctors sometimes prescribe ANTIVIRAL MED-
ICATIONS such as acyclovir for people who have six
or more outbreaks of herpes simplex infection in a
year or who have severe symptoms during outbreaks.
Herpes infections may involve the eyes or
the BRAIN, where they can cause permanent damage.
See also CANKER SORE; CHICKENPOX; COLD SORE;
HERPES ZOSTER; SEXUALLY TRANSMITTED DISEASE (STD)
PREVENTION; SEXUALLY TRANSMITTED DISEASES (STDS).
herpes zoster An INFECTION that results from
reactivation of the varicella-zoster VIRUS, which
lies dormant in the spinal NERVE roots after causing
CHICKENPOX. The virus can remain dormant for
decades; doctors do not know what reactivates it
though suspect a combination of aging and stress
to the IMMUNE SYSTEM. The infection travels the
tract of a spinal nerve to the SKIN, causing burning
or PAIN as it makes its way to the body’s surface.
Called the prodrome, this discomfort yields in
about two days to a rash of painful blisters that
erupts along the nerve’s pathway, called a DER-
MATOME. The blisters rupture in three to five days
and crusted sores form at the sites of the blisters.
Herpes zoster, also called shingles, occurs only
on one side of the body, most commonly on the
chest though may affect dermatomes anywhere on
the body. The blisters of the herpes zoster outbreak
can spread the virus, which can cause chickenpox
in people who have not had it or have not received
the varicella VACCINE. An uncomplicated outbreak
of herpes zoster runs its course in three to four
weeks, after which the virus again goes dormant.
Treatment with an antiviral medication taken at
the onset of pain but before blisters emerge (the
prodrome) can significantly shorten the course of
illness and decrease the severity of symptoms.
ANTIVIRAL MEDICATIONS TO TREAT HERPES ZOSTER
acyclovir
desciclovir
famciclovir
penciclovir
valacyclovir
Complications after the outbreak abates may
include damage to the eyes, loss of taste, and partial
PARALYSIS of the face when the outbreak
involves the trigeminal nerve. Post-herpetic NEU-
RALGIA is pain that persists along the dermatome
after the sores have completely healed, and may
be debilitating. Unlike its predecessor infection,
chickenpox, herpes zoster can recur though usually
does not.