What
causes genital herpes and what are the symptoms?
Most
cases of genital herpes are caused by genital infection with
HSV 2 a virus that almost exclusively infects the genital region.
HSV2 is the virus most associated with recurrent genital outbreaks
making it by far the issue facing most patients today.
Genital
herpes, whether a primary infection, or a recurrence, can exhibit
a variety of clinical symptoms. These range from the "classical"
symptoms of genital ulcers or blisters (referred to as "lesions")
on, or around, the genitals, to "atypical" symptoms such as
diffuse sores, reddening and irritation on the genitals, groin
or buttocks, pain on passing urine (dysuria), and a discharge
from the vagina. Infection may also be accompanied by a variety
of systemic symptoms such as flu-like symptoms (fever, headache,
and muscle pain) and tender, or swollen lymph glands, particularly
in the groin. These symptoms are more common with a primary
infection than with a recurrence.
Often, especially in recurrent cases, symptoms may be so mild
as to pass unnoticed or may be absent completely. When a person
has an outbreak with no symptoms, this is described as an asymptomatic
recurrence. Generally accepted figures for the occurrence of
typical, atypical and no symptoms are 20%, 60% and 20% respectively.
In other words, symptoms which are not "typical" of genital
herpes (atypical and no symptoms) are, in fact, the norm for
a genital herpes outbreak. Because of this, the majority (>85%)
of people infected with genital herpes are completely unaware
that they are infected. This has important consequences for
transmission of the disease.
During an outbreak, live virus may be produced ("shed") on the
skin of the infected person. This can then be passed to a sex
partner and might infect them. Since the symptoms of a genital
herpes outbreak can be absent, or so mild so as to pass unnoticed,
the virus can be transmitted without either partner knowing
they are infected.
Shedding of the virus without there being any noticeable symptoms
("asymptomatic shedding") occurs frequently in infected people
and is considered to be one of the main routes of transmission.
How
can I get diagnosed?
There
are two relevant tests for genital herpes, viral culture and
type specific blood tests .For patients who have sores or other
outward signs of infection -- what the medical literature calls
a "lesion" -- the most commonly used method is viral culture.
Viral culture looks for the presence of virus in the lesion.
Blood tests (serologic tests) detect herpes by looking for antibodies
in the blood or serum. Blood tests can be performed even when
no symptoms are present but you should ensure they are type
specific.
Viral
Culture
Prior to type specific serology, Viral culture was the "gold
standard" of laboratory testing for herpes and is still by far
the most widely available. The technique is similar to that
you may have seen in your high school biology class, when bacteria
are grown (cultured) in a petri dish. To perform a viral culture,
the doctor will use a sterile swab to retrieve a sample from
a lesion. A good swab will generally cause some discomfort when
a sore or lesion is sampled. The sample is sent to a laboratory
where it is grown for several days in a culture of healthy primate
cells. If the sample contains herpes, the virus will infect
the cells of the culture, causing cellular changes that can
be seen with a microscope.
However,
a poor sample may cause accuracy to drop. Even if herpes lesions
are present, there may be very little active virus left in the
lesions. In this case, the culture will come back as a "false
negative." That is, the test says there's no herpes even when
the patient has genital herpes. It's estimated that 20% of culture
tests produce a "false negative" when a patient has a first
episode of herpes. With recurrent episodes, when less virus
is present, the rate of false negatives goes up to 50%. It takes
anywhere from two to seven days to get viral culture results
back from the laboratory, which may mean several visits to your
doctor before a diagnosis is confirmed.
Type
specific serology
The new type specific tests, which distinguish HSV 2 from HSV1,
have been shown to contribute to patient management in almost
80% of all herpes cases, as they can be done when a person has
no symptoms and the sensitivity and specificity is better than
culture.
Most
cases of genital herpes are caused by genital infection with
HSV 2 a virus that almost exclusively infects the genital region.
Although genital infection with HSV 1 is also reported, up to
70% of the general population is infected orally with HSV 1
and serological tests for HSV 1 cannot distinguish between oral
and genital infection. Therefore unlike HSV 2 identifying genital
HSV 1 serologically is difficult as in most cases a positive
result may be due to simple oral infection. Indeed serological
testing for HSV 1 has been shown to be unhelpful in diagnosing
genital herpes (Munday et al 1998). Furthermore the many positive
tests that would be generated as result of widespread application
of HSV 1 serology to diagnose genital herpes could cause many
patients undue concern.
In
a situation where HSV 2 has been out-ruled as a cause of genital
herpes and HSV 1 is still suspected as a cause, the only reliable
method to confirm presence of the virus is a culture test which
should be done when lesions are present. HSV 1 serology has
some value in patient counselling as a negative result from
such a test does indicate naivety to the virus and such patients
may be advised that they are at risk of contracting genital
HSV 1 from oral genital sex. (Lafferty et al 2000)
The following table outlines the advantages
and disadvantages of genital herpes tests