Human Papilloma Virus HPV
Papillomaviruses are a group of
DNA-based viruses which affect the skin and mucous membranes of a
wide variety of animals. There have been detected more than 100
types of Human Papillomaviruses and it is estimated that
approximately 80 % of the population is infected with a strain of
HPV at some point in their life.
HPV strains or types are divided
into two categories. The first ones, the “low-risk” HPV strains that
can cause benign skin warts or papillomas, are transmitted through
the environment or by skin-to-skin contact. A separate group of
about 30 HPV strains are sexually transmitted. Some of them can
cause genital warts (such as types 6 and 11), others don’t have any
noticeable symptoms. Among the sexually transmitted HPV strains,
there is a group so-called “high-risk” HPVs (including types 16 and
18) which can lead to the development of cancer of the cervix,
vulva, vagina, anus, or penis.
In the United States the number of
patients identified with HPV disease has increased markedly during
the past 20 years because of heightened awareness of the various
manifestations of HPV disease and because of increased use of HPV
DNA testing. Approximately 7-10% of the population has nongenital
cutaneous warts.
Approximately 20 million people
are currently infected with HPV.The worldwide prevalence of HPV in
cervical cancer is 95-99.7% and in anal cancer is 88%.
The incidence of genital HPV
infection increases at the age when people begin to engage in sexual
activity (see figure). Most of the genital HPVs don’t have any
noticeable symptoms and are fought against and cleared by the immune
system in a couple of months. Nevertheless, in some cases, the
immune system may fail to bring the infection under control.
Lingering infection with “high-risk” HPV types, such as
HPVs 16, 18, 31 and 45, can
cause cervical cancer or other types of cancer. HPV types 16 and 18
are together responsible for over 70% of cervical cancer cases
(Baseman and Koutsky, 2005; Cohen, 2005). Type 16 causes 41 to 54%
of cervical cancers (Noel et al., 2001; Baseman and Koutsky, 2005)
and accounts for an even greater majority of HPV-induced vaginal/vulvar
cancers (Edwards et al., 2005), penile cancers, anal cancers and
head and neck cancers (Bolt et al., 2005).
SIGNS AND SYMPTOMS
“Low risk” HPV types usually cause no
symptoms at all or only one: genital warts.
Genital warts (also called
condylomata acuminata or venereal warts) are usually soft, moist,
pink, or flesh-coloured swellings that appear usually in the genital
area. They can be raised or flat, single or multiple, small or
large, and they sometimes look like cauliflower florets.
In women the warts occur on the outside and inside
of the vagina, on the opening (cervix) to the womb (uterus), or
around the anus. In men the symptoms of the disease may be less
obvious. When present, they usually are seen on the tip of the
penis. They can also be found on the shaft of the penis, on the
scrotum, or around the anus.After
sexual contact with an infected person, warts may appear within
weeks or months, or not at all. Genital warts can rarely develop in
the mouth or through of a person who has had oral sex with an
infected person.
Genital warts are very contagious.
If you have an active outbreak of genital warts, it is best to
refrain from any sexual activity until the warts have been treated.
It is very important to remember
that HPV strains that can cause genital warts are NOT the
same ones that cause cervical cancer!
TREATMENT
Currently, there is no cure for
HPV infection. In most cases the immune system manages to clear the
infection. The treatments available are directed to the effects of
HPV on the skin or the mucous membrane. The treatment varies
depending on several factors such as the size and location of your
genital warts. Some of the medicines used to treat genital warts
are: Imiquimod (an immune response modifier), Interferon alfa
(cytokine), Podofilox (an antimitotic drug), Podophyllin (resin
derived from the Mayapple), 5-Fluorouracil (antimetabolite
interferes), Keratolytics (TCA and BCA).
If the warts are small they may be
removed by freezing (cryosurgery), burning (electrocautery) or laser
treatment. Bigger ones that have not responded to treatment can be
removed by surgery.
COMPLICATIONS
Approximately 10 of the 30
identified genital HPV types (including types
16, 18, 31 and 45)
can lead, in rare cases, to development of cervical cancer as well
as anal cancer, vulvar cancer, head and neck cancers, and penile
cancer.
Cervical cancer is the second most
common type of cancer to affect women. However not all strains of
genital HPV can cause cervical cancer. The ones that cause genital
warts are extremely rare associated with this type of cancer.
Women who have genital warts
during pregnancy may pass the warts to the child if they have an
active outbreak, especially during a vaginal birth. HPV then
develops in the child’s throat and it can be life threatening.
PREVENTION
On June 8, 2006, the FDA approved
Gardasil, a prophylactic HPV vaccine which is marketed by Merck.
This vaccine was shown to be effective against initial infection
with HPV types 16 and 18 (some of the HPV strains responsible for
cervical cancer).
People with a greater number of
sexual partners are more exposed to HPV infections. A way to prevent
becoming infected with HPV is to reduce the number of sexual
partners. Recent studies have shown that the condom offers little
protection against this sexually transmitted disease. There are
however some momentary solutions like topical microbicides or
some sexual lubricant brands
that use a gelling agent called carrageenan.
A way of preventing cervical
cancer is to regularly have a
Papanicolaou screening, colloquially known as "Pap"
smear testing. This can also help prevent anal cancer. Also, it has
been scientifically proved that tobacco smoking increases the risk
of developing invasive cervical cancer and other HPV-induced cancer
types. Smoking decreases the ability to absorb folic acid (used to
treat cervical dysplasia, a symptom of HPV infection).
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