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What is human papillomavirus (HPV)?
HPV
is a group of small DNA viruses that cause warts and certain cancers
and precancers of the skin lining the lower genital tract and mouth
Approximately
100+ types have been fully identified. Another 30 "novel"
types have been detected but not fully identified. All differ
slightly from each other in their genetic structure.
This
difference in genetic structure determines the location and the type
of lesion that each type is likely to cause.
23-30
types infect almost exclusively the skin of the lower genital tract.
The remaining types infect skin on other areas of the body,
including the hands, feet, etc.
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What
are low- and high-risk HPV types?
The
genital HPV types can be divided into two broad groups (low-risk and
high-risk HPVs) depending upon their association (or lack of
association) with cancers of the lower genital tract.
Low-risk
HPV types (6, 11, 42, 43, 44, 54, 61, 70, 72, and 81) are virtually
never found in cancers. Therefore, they are also called
non-carcinogenic HPV.
High-risk
HPV types (16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 68, 73,
and 82) have been identified in cancers of the cervix, vagina,
vulva, anus, and penis. Therefore, they are also called
carcinogenic HPV.
The
most common types (>
90%) detected in genital warts are HPV 6 and HPV 11.
The
most common HPV type detected in both normal women and in women with
cervical cancer is HPV 16.
The
majority of cervical cancers (80%) are caused by just 4 HPV types
(16, 18, 31, and 45).
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How
common is HPV?
Genital
HPV is very common. It is the most common viral sexually transmitted
infection (STI) and is likely to be the most common STI overall.
Many
estimates have placed the lifetime likelihood of getting genital HPV
to be in the range of 75-90%.
The
risk of exposure to HPV is estimated to be approximately 15-25% per
partner.
Most
people who get HPV never know they have it, as they do not develop
genital warts, an abnormal Pap test, or other manifestations of HPV
that they can identify.
Approximately
1-2% of the population has genital warts and the lifetime risk is
estimated to be about 10%.
Approximately
2-5% of women have a Pap test with cell changes due to HPV at any
one screening.
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What are the symptoms of HPV?
HPV rarely causes symptoms.
External genital warts are most commonly felt as raised bumps, but may be so
small that they often go unnoticed.
Occasionally
newly forming warts and vulvar intraepithelial neoplasia will be
slightly itchy, but most HPV lesions do not cause soreness, itching,
burning or any other symptoms. When those symptoms occur, look for
other causes such as yeast or irritation from soaps or spermicides
that may cause these symptoms whether or not warts are present.
Certain
symptoms may occur with cervical cancer and should be evaluated.
These include bleeding during or after intercourse, irregular
vaginal bleeding between periods, and a persistent abnormal
discharge without itching or burning. However, these symptoms most
often occur for other reasons.
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What
can genital HPV cause?
Most
people who get HPV do not get significant lesions.
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How
is HPV transmitted?
HPV
is primarily transmitted through genital skin-to-genital skin sexual
contact.
Penetrative
intercourse is not required.
The
exact risk of developing genital warts after having one episode of
sexual intercourse with someone who has genital warts is not known,
but several studies would appear to establish a risk in the range of
65% or more.
Likewise,
most studies of women with cervical HPV disease indicate that
approximately 64-70% of their partners will have HPV penile lesions
if evaluated clinically. Most often, these are so small that neither
partner is aware of their presence.
The
most common time interval from exposure to HPV to development of
genital warts is 4 weeks to 8 months. However, HPV can remain latent
in some people for years or decades before developing warts or
cervical disease, so it is usually not possible to determine exactly
when, or from whom, an individual contracted the virus.
When
one partner has HPV lesions caused by a particular virus type, it is
most likely that the other partner shares the same virus type,
although this is often impossible to prove. Several studies indicate
that "shared HPV" does not "ping-pong" back and
forth. There is evidence that using condoms may decrease the viral
exposure and speed the clearance of HPV related disease. The
decreased viral load may allow the individual's own immune system
a better chance of eliminating the virus.
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Can
HPV be passed through oral sex?
Yes.
Most
couples practice oral sex, yet HPV lesions are very uncommon in the
mouth. However, recent studies report high-risk HPV in
approximately 1/4 of squamous cell carcinomas of the head and neck
worldwide, so oral HPV transmission does occur but only very rarely
causes serious problems.
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Can
HPV be passed in any other way?
There
is no evidence that contaminated toilet seats, doorknobs, towels,
soaps, swimming pools or hot tubs, can transmit HPV. However, some
unexplained cases of HPV lesions do occur and one should never rule
out the possibility that an HPV infection may have been transmitted
in a non-sexual event.
HPV
types that cause hand and common warts are different from the types
that cause warts in the genital area. The exception is the rare
occurrence of warts in the genital area in young children that are
due to these "non-genital" HPV types. Likewise, genital
HPV types are only very rarely found in lesions outside the genital
area. For instance, occasional HPV 31 lesions have been described in
the conjunctiva and under the finger nails .
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Can
I infect my baby?
Transmission
to the baby of HPV 6 or 11 is known to be possible during vaginal
delivery but is rare. Most clinicians believe that the risk of
cesarean section to both mother and baby exceeds the risk of the
baby acquiring laryngeal papillomatosis (HPV 6 or 11 induced warts
in the larynx or upper airway).
Once
warts are no longer present, especially if a woman has had no
detectable HPV lesions for 6 months or more, transmission of HPV to
the baby during vaginal delivery becomes increasingly unlikely.
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Will
I be contagious after I am treated?
That
depends on two things - how successful the treatment is in
destroying the HPV lesions (where potentially infectious HPV
particles are known to be present), and how successful one's
immunity is in suppressing any HPV that might still be present in
apparently normal skin.
Most
people treated for external warts do not have complete resolution
even after several treatments. That is because most treatments
destroy the HPV lesions but cannot eliminate any HPV in surrounding
apparently normal skin. Until the individual's immune system
responds and suppresses the remaining HPV, new lesions may appear.
Once
no further HPV lesions can be detected by clinical exam, and no new
lesions have appeared over several subsequent months, the chance of
shedding enough HPV to be contagious dramatically falls. While it is
impossible to tell anyone exactly when they have little-to-no chance
of passing HPV to a partner, as months go by with no lesions found
(especially if none are found by a skilled clinician), the
possibility of being contagious becomes increasingly remote.
The
inability to be 100% sure that an individual with a history of an
HPV infection is no longer contagious should encourage honesty
whenever a new relationship begins. This should be balanced with the
fact that most people are exposed to this virus during their life,
and that, for most, this virus does not usually cause great harm.
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Will
I be contagious if I have spontaneous immune regression?
How
can I reduce the risk of getting HPV?
The
only way to entirely eliminate the possibility of beingexposed to HPV
is abstinence from any form of genital-genital or oral-genital
contact.
An
HPV vaccine (Gardasil®) was introduced in 2006 . The HPV vaccine
presently available protects against the exposure to types 16,18,
6,and 11 The vaccine is FDA approved for girls and women 9-26 years
of age and is highly protective, especially when the vaccination
occurs before sexual activity. While the vaccine does not prevent
infection with all types of HPV, it provides protection against the
HPV types associated with 70% of cervical cancers (16,18), and 90% of
external genital warts (6,11). The vaccine however does not protect
against HPV 16, 18, 6 or 11 if a woman has already been infected with
these types, and it offers limited or no protection against other HPV
types. The
protection afforded by the vaccine is therefore lower in women who
have had sex prior to vaccination. Hence,
the
primary target for HPV vaccination is girls age 11 & 12 but it
may be given as early as age 9, particularly in populations with
early onset of sexual activity. Catch-up vaccination is also
appropriate for girls and women age 13-26.
A bivalent vaccine that protects against HPV 16 and 18 (Cervarix ®)
is expected to be on the market in the US by 2010, and is already in
use in Europe and other areas of the world.
Latex
condoms protect only those areas of skin that they cover. Many
infected individuals have HPV in areas of their skin that are not
covered by the condom and that come into contact with their
partner's skin. Secretions may also be a source of HPV-infected
skin cells that could contact a partner's uncovered skin areas.
Despite these issues, recent data indicates that consistent condom
use appears to reduce the risk of HPV transmission by about 70%.
If
a sexual partner has ever had sex, even once, with someone other
than their partner, their partner may be at risk for contracting HPV
or other STIs. Hence, it is prudent for couples contemplating
starting a new relationship to test for STIs prior to prudent for
couples contemplating starting a relationship to be screened for
STIs before having sex. However, because HPV is so very common and
most often not detectable, clinical exams for HPV as part of a STI
screen have not been recommended by the CDC or AMA.
Condoms
do offer some protection against HPV and very good protection
against other STIs. Use them.
Female
condoms cover more of the female introital epithelium at risk for
HPV and therefore may be a more protective barrier for both
partners. However, the female condom may also be more easily
dislodged.
Spermicidal
foams, jellies and creams are not proven, nor are they disproved, to
be effective against HPV but they have been shown to be effective
against some other STIs. Recent studies in Africa have shown an
increased rate of acquisition of HIV when spermicides are used with
an HIV-infected partner. If used, spermicides are best used along
with condoms, not in place of condoms.
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Why
do most people not have a lesion detected after being infected with
HPV, while others get warts or CIN, and a few get cancer?
Although
this question cannot be answered fully, science is steadily
improving on our understanding of how HPV causes both warts and
cancer.
HPV
infects the skin when cells from a partner's HPV lesions gain access
to tiny breaks in the skin that often occur during skin to skin
contact or intercourse. HPV does not infect tissue that lies
underneath the skin, nor does it infect blood or other body fluids.
After
an average of 1 to 8 months (but up to years or decades) the HPV
infected cells may start to grow abnormally as the virus begins to
reproduce itself in large numbers. Whether this occurs at all, and
if so, how it is manifest clinically, is largely the result of a
complex interplay between the virus and individual immunity.
For
most individuals the immune response appears to dominate and lesions
never develop, or they develop but are suppressed by an immune
response before the person ever realizes the presence of the
lesions.
Escape
from immune suppression of a low-risk HPV type (i.e., 6 or 11) most
commonly results in epithelial changes as well as exuberant growth
of both underlying blood vessels and stroma. The result is raised
"cauliflower" shaped warts. In contrast, similar "escape"
of high-risk HPV types (i.e., 16 or 18), results mostly in
proliferation of the epithelial (skin) cells with only minimal
vascular or stromal growth.
Treating
HPV infected cells may help boost immunity by destroying the cells
within which the HPV resides, thereby releasing HPV to
disease-fighting dendritic cells and macrophages. A cream which is
applied to warts (imiquimod or Aldara®) may directly boost
immunity by stimulating these disease-fighting cells to produce
natural disease fighting chemicals (cytokines, including
interferon).
Even
left untreated, most HPV lesions would eventually disappear due to
an immune response, although spontaneous clearance may be very slow
for some. However, approximately 10-20% of individuals with HPV
lesions do not clear easily, even with treatment.
Long-term
persistence of HPV is not very common. When it happens, the complex
interplay of HPV, host immunity, various co-factors, and perhaps,
spontaneous mutations in the host cell may eventually result in the
development of pre-cancers and cancer of the cervix, vagina, vulva,
anus, or penis. Because an individual's immune system can usually
suppress (and perhaps even clear) HPV most individuals are not at
great risk of getting these cancers.
Once
immunity has completely suppressed a particular HPV, the individual
is not likely to again get disease from that HPV type, either from a
recurrence of the HPV infection one has already had, or from new
exposure to the same HPV type. However, immunity to one HPV type
does not confer reliable immunity to a different type.
One
study showed post-treatment women fared better with partners wearing
condoms.
How
to reduce the risk of CIN? Stop smoking.
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Will
I always have HPV?
The
answer to this question is not clear.
Most
people (up to 90%) who test positive for HPV with very sensitive
tests for HPV (polymerase chain reaction [PCR] and Hybrid Capture 2)
will become HPV negative on the same tests within 6 to 24 months
from first testing positive. This is due to an effective immune
response to HPV.
What
is not known is whether this means that the virus is actually
eliminated from the body or just suppressed to such a low number of
HPVs (as in latency) that even these sensitive tests cannot detect
it.
Whether
it is completely eliminated or just suppressed does not matter
because most people who have an effective immune response to HPV do
not ever have lesions develop from this HPV infection.
A minority of people may be at-risk for having return of warts or
other HPV lesions later in life, usually if immunity is seriously
compromised.
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