Overview of the Etiologic Agent
The herpes simplex virus (HSV) is a double-
stranded DNA virus. It is a member of the
human herpes viruses (herpetoviridae) group. This
group includes varicella zoster virus (chicken
pox) and Epstein-Barr virus (the virus that causes
mononucleosis), among others. There are two types
of herpes simplex virus, types I and II. Both HSV
I and HSV II can be considered STDs, since they
both can be transmitted sexually and both can
cause lesions in the genital area. HSV II causes
70 to 95 percent of genital herpes infections.
The remaining 5 to 30 percent of genital herpes
infections can be attributed to HSV I.
According to a survey of 40,000 Americans
conducted between 1988 and 1994, the overall HSV
II prevalence rate in the United States is
almost 22 percent. Genital herpes is the most
common cause of genital ulcers in the world, with
20 million cases diagnosed annually. Unprotected
sexual activity, particularly with multiple
partners, and being female increases your risk of
acquiring HSV II. There are also increased rates
of HSV among African American and Latino
populations, and those in lower socioeconomic
groups.
Transmission of HSV occurs during oral, vaginal,
or anal sex when an infected partner passes on the
virus through microabrasions in his or her
partner's skin or mucosa. The person passing
on the herpes needs to be shedding the virus at
the time of contact with his or her partner.
Typically viral shedding occurs when the infected
person is experiencing an outbreak of lesions.
However, viral shedding can take place before a
lesion erupts, or can take place in the absence of
lesions; this is called "asymptomatic
shedding." The rate at which an infected person
sheds the virus is entirely dependent on the
individual, but some studies have shown that an
infected person may be shedding the virus
asymptomatically 1 out of every 4 days.
Once an epithelial cell is infected in another
person, the virus replicates at a high rate.
Inside the body the virus invades sensory nerves
and takes up residency for the life of the host in
their sensory nerve cell bodies in the dorsal
root ganglia. Initial infection causes symptoms
(see below), but once these symptoms are resolved,
the person is at risk for later recurrence of an
outbreak.
Signs, Symptoms and Treatment
Primary infection refers to an initial infection
with HSV. Fifty to 70 percent of people will
develop a fever, aches, and headache in addition
to symptoms in the genital region. Genital
symptoms may begin as pain, itching, painful
urination, vaginal or urethral discharge, and
lymphadenopathy and progress to the
development of characteristic lesions. The
lesions first appear as red bumps or blisters,
which evolve into ulcerations before crusting
over. They are often painful. At the onset of
the infection, the person will be infectious and
shedding the virus for up to twelve days. These
lesions may appear on the penis, scrotum,
buttocks or anus in a man, and on the labia,
in the vagina, on the cervix, and on the anus
or buttocks in a woman. The lesions may take up
to three weeks to heal.
Lesions can also occur on the lips or in the mouth
of a person through exposure to oral sex. Lesions
that only occur orally on a person may be
attributed to HSV I infection, and exist in the
absence of having HSV as an STD. HSV I prevalence
in the U.S. population is, in fact, widespread.
Over 90 percent of adults will be infected with
HSV I by the fifth decade of life. There is
evidence that prior infection with HSV I lessens
the severity of an initial infection with HSV II.
When lesions occur on or around the eye, they
should be taken very seriously, as they can cause
serious damage.
Recurrences occur when the virus is reactivated in
the dorsal root ganglia and replicated, traveling
down the peripheral sensory nerve pathways to the
skin where new symptoms may or may not occur. In
the absence of symptoms in a recurrence, the
person may asymptomatically shed the HSV.
Outbreaks due to recurrences are usually more mild
and of shorter duration than primary infection.
Recurrences are triggered by unknown and known
factors. Known factors include exposure to
sunlight, fever, trauma, diminished cellular
immunity, and emotional stress. The numbers of
recurrences per year vary widely per person, but
on the average occur 2 to 6 times a year.
Complications of genital herpes infections include
aseptic meningitis and disseminated
infection, among others. The disease can be
passed from mother to child during birth, and
neonates are at high risk for disseminated
infection when this occurs.
Health care providers usually make the diagnosis
through visualization of herpetic lesions, but
there are a variety of diagnostic tests that help
identify and determine the type of herpes virus.
Tests include culture, antigen detection tests
and blood tests. Even if a test result is
negative, the person cannot rule out having the
disease, since obtaining a specimen (particularly
for culture) is often difficult.
As herpes simplex is a virus, there is no
effective antibiotic therapy. Treatment of the
symptoms of herpes with pharmacologic
therapies may shorten the duration of outbreaks,
particularly if administered soon after the onset
of symptoms. Some people may decide to go on
long-term therapy to suppress recurrences.
