Herpes
simplex virus is still a mystery for researchers and physician because they
have yet to explore many things about it. The word ‘Herpes’ have its origin in
Greek language and means ‘to crawl or to creep’, a name perfectly suited
because once the cells are infected, the virus ascends the nerve pathways to
reach dorsal root ganglia and lie dormant there, only to resurface and cause
infection sporadically.
Besides Herpes
Simplex that causes sexually transmitted diseases, other common Herpes strains include
chicken pox or shingles (caused by herpes zoster virus) and Kaposi’s sarcoma
(caused by herpes virus 8).
Herpes simplex
primarily infect mouth and genitals and spread by bodily fluids. Two type of
Herpes Simplex Viruses are commonly seen in clinical practice: herpes type
1 (HSV1) and herpes type 2 (HSV2).
Herpes Virus
type 1
HSV1 is highly contagious infection. It is endemic throughout the globe but the age of primary infection varies according to geography. In African subcontinent majority of infection is acquired in childhood while in America, Europe and western Pacific seroconversion continues well into adulthood.It is mainly transmitted by oral-to-oral contact to cause oral herpes infection via infected sores, body fluids or surfaces. The oral lesion is commonly
known as cold sores, however it can cause genital herpes due to oral-genital
contact too.
A person who
has a history of HSV 1 oral herpes infection is unlikely to get HSV1 genital
infection in future, but he /she is still at risk of getting HSV2 genital infection.
If a person with Genital Herpes tests positive for HSV1, then there is less chance of infecting the partner The frequency of sporadic shedding and recurrence is much less too in HSV type 1 infection.
HSV1 is
vertically transmitted from mother to fetus if the women acquire genital infection
for the first time in late pregnancy. Risk of transmission is very less if she
was already infected before pregnancy. She should inform her obstetrician if
she gets infected late in pregnancy.
In HIV,
infected population HSV1 is known to cause more serious infections and frequent
recurrences due to Immunocompromised state. Sometimes, it can cause keratitis
and encephalitis.
Herpes Virus
type 2
HSV2 is also a global issue, it is exclusively transmitted sexually, causing genital ulcers or
blisters. Its prevalence is highest in African subcontinent where nearly 32% population
is harboring the virus. More women are infected with HSV2 than men because men
to women transmission is more efficient than women to men.
After the
first infection and seroconversion, recurrent infections are mild and
infrequent, decreasing over time.
It is primarily
transmitted through sexual contact with sores, ulcers or bodily fluid of an
infected person. Rarely, vertical transmission has also been documented.
People infected
with HSV2 are at 3 times higher risk for getting HIV infection. About 60-90% of
HIV infected people are also test positive for HSV2.
Contrary to
the popular belief that Herpes 1 only infect above the waist and Herpes 2
infect below the belt, Herpes 1 is perfectly capable of causing genital
infection and more than half of new genital herpes cases are caused by type1. Similarly,
Herpes type 2 can cause cold sores.
According to
a 2012 fact sheet by WHO, globally 3709 million (67%) people aged 0-49 have Herpes
type 1[1]
while 417 million (11.3%) people aged 15–49 years have Herpes type 2.[2]
Almost 1 in 6 people in US, aged 15-49 years have Herpes type 2 infection and
most people are unaware of it because the symptoms are very mild.
Herpes is a
lifelong infection with mild or no symptoms at all making it difficult to
estimate the burden of disease. The virus remains dormant in the dorsal root
ganglia for unknown period of time and becomes active again and resume
shedding. About one-third to half of people who shed virus have no symptoms at
all and are being responsible for 70% of transmission.
Both Herpes
1 and 2 can cause cold sores and genital infection but majority of cases of
cold sores are caused by Herpes1 and majority of genital infections by Herpes2.
This is very important from the point of recurrence, because if Herpes 2 causes
you cold sores, it is far less likely to recur and shed the virus sporadically and
same holds true for Herpes 1 causing genital infection. They do best when they
are in their natural habitat.
The initial
orolabial and genital blisters are very severe and subsequent attacks are often
very mild and may not cause any symptoms also.
Treatment
consists of antivirals like acyclovir, famciclovir, and valaciclovir. They only
reduce the severity of symptoms but do not cure the infection.
‘Prevention
is the best cure’ paradigm holds good for Herpes Simplex infection. Using
barrier methods for protection along with abstaining from sex during symptoms
of genital herpes reduces the risk of transmission. Vertical transmission can
be prevented by sharing information with the obstetrician. Males undergoing
circumcision are at 50% less risk of infection with HSV2, HIV and HPV.[3]
Research is
underway to develop vaccines or topical microbicides to prevent the spread of Herpes.
Herpes and
Pregnancy:
According to
ACOG
Women who
have genital herpes infection late in pregnancy and have a vaginal birth have
30-50% chances of infecting the fetus.
First
episode occurring late in pregnancy also have high chances of vertical transmission
as opposed to recurrent infection (2-5% chances).
Neonatal infection
with Herpes simplex occur in 1in 3500-10,000 livebirths in USA, mostly to those
women with asymptomatic or unrecognized infection.
Maternal infections are classified into:
- Genital
infection is labelled as ‘primary’ when the patient is seronegative for both
HSV-1 and HSV-2.
- It is
labelled as ‘nonprimary first’ when it occurs in patient with prior history of heterologous
infection (HSV2 in patient who had prior HSV1 infection and vice versa).
- Recurrent
when it occurs with clinical or serological evidence of prior genital herpes.
Misconceptions
are rife among physician, researchers, laboratory personnel and patients about ordering
and interpreting lab reports for Herpes.
That is the topic for next
article on the blog.
[1] http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0140765
[2] http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0114989
