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Volume CXXXIII, Number 17 |
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Been wearing your flip-flops?
JEFF BENSON, M.D.
Dear Dr. Jeff: Are warts contagious when they're not
in the genital area? W.L.
Dear W.L.: Warts, or "verrucae," are a type of
viral infection of the skin. They are a very common dermatologic problem,
second only to acne, and affect at least three out of four people at some
point in their lives. Warts are caused by human papillomaviruses ("HPV"),
of which there are more than 70 subtypes. All HPV incorporate their DNA
into infected cells and may remain in our bodies for life. During times
of physical or emotional stress, when our immune systems are weaker, viral
proliferation can begin and warts appear.
Verrucae are classified according to location. Different
viral subtypes have marked predilections for different types of skin,
and thus different parts of the body. Common, elevated warts ("verrucae
vulgaris") typically appear on the hands. Of the eight HPV subtypes
which cause the vast majority of common warts, seven rarely, if ever,
cause genital lesions. The notable exception is HPV-2, which causes not
only a great many common warts, but also oral and genital warts as well.
Other HPV infections cause flat warts ("verrucae planae"), usually
appearing on the face and legs. Genital warts ("condyloma")
are, of course, found in the anogenital areas, and may be mutagenic. Callus-covered
plantar warts ("verrucae plantaris") occur on the soles of the
feet.
Humans are the only known reservoir of HPV. Contrary to
popular belief, no other animals, including toads, either carry or transmit
the virus. Transmission of HPV likely occurs through direct contact with
infected people, with objects they have touched, or with sloughed, infected
skin cells. The virus presumably enters through small breaks in the skin.
Plantar warts, for instance, are thought to be contracted most often from
contaminated floors in swimming pools and communal showers.
Direct person-to-person transmission of non-genital warts
is relatively inefficient and unlikely. The incubation period after inoculation
is unknown, but is probably no less than several months. The latency period
for genital warts may be particularly long. Autoinnoculation of HPV from
one part of the body to another can also occur.
Most non-genital warts disappear on their own without treatment
(up to 80 percent within two years). Warts can be bothersome, however
(and two years can be a long time!). They can bleed and cause pain if
bumped, and they can also seem embarrassing. Treatment of warts may decrease
the chance that they'll spread to other areas of the body or to other
people.
Common and plantar warts are often effectively treated with over-the-counter
remedies. Flat, facial warts, and genital and oral warts are usually treated
in a medical office, using "ablative" or "medical"
therapies. Ablative treatments include surgical excision, destruction
by electrodessication, laser or liquid nitrogen, or chemical "peeling"
with cantharidin or podophyllin.
Topical medical treatments include daily applications of
cytotoxic or antiviral agents, such as 5-fluorouracil, retinoic acid,
or podofilox. Some dermatologists apply immunotherapy agents to warts,
such as DPC haptens or even poison ivy oils, in hopes of inducing a controlled
allergic reaction and provoking peeling. Recalcitrant warts are sometimes
treated with interferon injections to boost the immune response to the
HPV infection.
Innumerable "alternative" remedies for warts have
been tried over the ages, with varying degrees of success. With the important
exception of anogenital warts, there's no reason to rush in for "high
tech" medical treatment.
As always, though, all of us at the Health Center are happy
to see you and discuss any questions or concerns you might have.
Be well! And wear your flip-flops in the showers and locker
rooms!
Jeff Benson, M.D.
Dudley Coe Health Center