Human papilloma viruses (HPVs) cause warts in people -- whether
on the skin or on mucous membranes. There are over 100 identified
types of HPVs. HPVs grow only in humans, and no other
causes of warts have been found (it is not possible to get a
wart from touching a frog, regardless of folklore). Some HPV
types grow best in skin, while others grow best in mucous
membranes. Some types grow only in skin or in mucous membranes,
but there are a few which can grow in both places although they may
prefer skin to mucous membranes or vice versa.
The most common HPV infection is a wart on the skin.
Common warts are rough, hard lumps or plaques (flatter
lesions) with a rough, irregular top surface. They are found
mostly on the back of the hand or the top of the foot, between
fingers or toes, near fingernails or toenails. They can also be
seen on mucous membranes. Like all skin warts, HPV causing common
warts is transmitted from an infected person, usually by
skin-to-skin contact although viral particles may be left on
objects (such as shower-stall floors or gym equipment) and picked
up by someone else touching the object. It is possible for HPV to
infect unbroken skin, but broken skin certainly makes it easier
for HPV to enter, and people with
eczema or who
have certain kinds of immune problems (such as those caused by
AIDS or induced in organ-transplant recipients by antirejection
drugs) are more likely to be infected. It takes 2-6 months after
exposure to HPV to develop a wart.
Although common warts can be found on palms or soles, warts on the
palms or soles, known as plantar warts (not
"planter's warts, by the way -- "plantar" is the term we use to
refer to the sole of the foot) are usually thick and painful, and
are often covered by a thick callus (a layer of thick and hard
skin). The skin ridges that make up your fingerprints and hand
prints are obliterated on the wart surface. If the callus and the
top of the wart are shaved off with a razor blade you may see
bleeding from tiny blood vessels within the wart tissue. (Often we
have to shave off part of the wart to be able to do anything else
to treat it.)
There are also flat warts, also known as "juvenile warts" because they usually appear in kids. They are papules (raised bumps) with irregular margins but with smooth surfaces, and are often seen on hands, the face, and the neck.
These warts are annoying, but they are usually benign (although
there are some very rare conditions in which skin warts can
lead to skin cancer).
HPV, Condylomas, and Cancer
The more important problems occur with HPV infections of mucous membranes, especially those of the genitals in both men and women. According to the US Centers for Disease Control and Prevention (CDC), HPV is the most commonly seen STD (sexually-transmitted disease) in the United States.
The most common genital HPV lesion is condyloma acuminata, in which papules appear on a man's penis; on the surface of a woman's vulva (the area inside the labia majora and surrounding the clitoris and the opening of the vagina), the mucous membrane wall of the vagina, or the cervix; around the anus; and/or on the perineum (the skin between the anus and the bottom/back point where the labia meet in women or the base of the scrotum in men). The papules may be tiny (>1 millimeter) but may be much larger, especially if several have coalesced to form a large lesion. They may be pedunculated (a stalk with a knob or ball at the end), and the tissue is thickened and may look more like skin than like mucous membrane; they may be skin-coloured or a bit grayish. Most people with condylomas do not feel anything out of the ordinary at the site of the lesions, but some may be tender, itchy, or burning. Circumcised men with condymonas usually have them on the shaft of the penis, while uncircumcised men's condylomas are usually inside the foreskin (either on the inner layer of foreskin or on the head of the penis itself). Condylomas in women are most often found at the far end of the vagina, either on the cervix or on the vaginal wall; they can also be seen commonly on the labia majora or the labia minora. There are also giant condylomas, often seen on the head of the penis, on the foreskin, or around the anus; these are large and resemble a cauliflower.
The problem with condylomas, and with HPV in general, is that
infection in these areas with HPV puts a patient at risk for cancer
in that area. HPV infection of the cervix is the most frequent
cause of cervical cancer: up to 15% of women with genital HPV
infections will develop cervical cancer or precancerous cervical
lesions in 2-3 years if not treated. Since HPV is passed from
partner to partner during sexual activity, and since many men
(especially those with small papules on their penises) don't know
they have HPV, the risk of being infected increases with the number
of partners a patient has had sex with, and with the number of
partners that the patient's partner has had sex with. My colleagues
and I routinely see teenage women (as young as 14-15 years) with
precancerous cervical changes.
Another -- and fortunately still rare -- problem caused by HPV is
the development of papillomas, or mucosal lesions, in the
mouth, throat, larynx (voicebox), and trachea (windpipe). This
happens most often in a baby who is born vaginally and whose mother
has a genital HPV infection, but delivering the baby by Caesarian
section does not seem to reduce the chances of respiratory
papillomatosis by very much. It is also possible for an adult or
adolescent to develop respiratory papillomas by receiving oral sex.
The papillomas are frequently found in the larynx, but they have
been seen in the trachea and even in the lungs.
How do we treat HPV infections? Unfortunately, it's not that easy,
since there are few
antibiotics available for HPV. We can get rid of the warts
themselves, but if the virus is still present it's very likely to
come back. Also, since skin is pretty tough and the epidermis
(the outermost layer) is made up of dead cells from the lower layers,
it's hard to eradicate the infected tissue completely, especially if
the skin is dry and intact.
Treatment of Skin Warts
There are several methods available for removing skin warts -- or at least making then smaller. Many of them involve destroying the wart tissue. This can be done by:
Some of these treatments are available over the counter; however, you
should talk to your doctor before using any treatment.
Treatment of Condylomas and Cervical HPV
Treating genital and anal HPV infections is a different matter. The
most effective treatment for condylomas is to destroy the infected
tissue, as it is for skin warts; this can be done by cryotherapy, by
burning the infected tissue with a laser or an electrical cautery,
by cutting the entire condyloma out, or by applying chemicals (most
commonly podophyllin) directly to the wart. Except for
podophyllin, which is available by prescription (and much less
concentrated) for home use, all of these treatments must be performed
by your doctor. Cervical changes can be detected early enough to
allow destruction of the affected tissue, but this requires that a
woman has regular pelvic exams and Pap smears (which is the primary
way to detect cervical cancer or precancerous changes).
Treatment of Respiratory Papillomas
Respiratory papillomas pose a different treatment problem. Because
of their location, they can compromise breathing if they become large
enough. Therefore destroying the papillomas (usually with a laser)
is the practical treatment. However, since the virus may still be in
nearby tissue, the papilloma is likely to come back -- in which case
it may have to be destroyed again. And again. And again. A child
with a respiratory papilloma may require laser "ablation" of the
papilloma every 3 months or so for life.
Preventing HPV Infections
The easiest and most effective way to prevent HPV infections is to avoid contact with other people's infected lesions or with any objects that might have HPV particles on their surfaces. This can be a problem, especially in communal living situations (dorms) and gyms and health clubs. Wearing slippers or shoes in public showers may help prevent picking up HPV from the shower floor; many health clubs provide disinfectant sprays with which you can wipe down equipment before and after using it. If you have a wart it is polite to avoid touching someone else with the open wart.
Avoiding genital and anal transmission is more difficult. The only
certain way to avoid trasmission is to avoid sexual contact with an
infected or potentially infected partner. HPV can be passed on
through foreplay and during activities not involving vaginal contact
(as noted above, receptive oral sex may lead to respiratory
papillomas). Condoms may help a little, but it's possible for HPV
from warts or condylomas on a man's scrotum to make it to his
partner's vulva by direct contact, then to the outside of the condom,
and from there into the vagina. (Similar considerations apply to
anal sex.) Since it's possible for a person with HPV to be contagious
before the lesions appear, mere examination of a new partner isn't an
absolute guarantee. As with all STDs, the risk of being infected
with HPV increases with the number of partners you have and the
number of partners your partner(s) has.
The New HPV Vaccine
There is now a vaccine available for four types of HPV: types 6, 11, 16, and 18. Type 16 is found in about half of all cases of cervical cancer, and type 18 in about 1/5 of cases. Types 6 and 11 are found in 80% of genital warts and respiratory papillomas. The vaccine is given as a 3-dose series, with the second and third doses given 2 and 6 months after the first dose, and can be given to women between ages 9 and 26 (at least so far). It should not be given to someone who is pregnant. The Advisory Committee on Immunization Practices recommends that it be given to 11- and 12-year-old girls, although it can be given to women as old as 26. The four-strain vaccine is also now recommended for boys and young men (age 9-26 years) and has been shown to prevent most (but not all) genital warts in males. A two-strain vaccine which protects against types 16 and 18 HPV is also available; it protects against cervical precancer lesions but not against genital warts, and is recommended for girls and women age 10 to 25 years.
Although the vaccines can reduce the risk of cervical cancer in women
who are already sexually active, they are most valuable as a preventive
measure if given to someone before she becomes sexually active. (It
does not appear to help a patient who is already infected with one of
the covered HPV types, but it will still protect the patient against
the types she has not yet been exposed to.) Studies so far show that
immunity lasts for at least 5 years. It will not protect someone
against types of HPV other than 6, 11, 16, and 18, and it will
certainly not protect against other STDs -- condoms are still a very
good idea, being choosy about partners is a good idea, too, and
abstaining from sexual activity is still the only certain way
to prevent all STDs.
For more information on HPV and the new vaccine, see the CDC's HPV Web site.