Doc: wear flip-flops
Dear Dr. Jeff: Are warts contagious?-W.L.
Dear W.L.: Warts are caused by a viral infection of skin cells. They are very common, second only to acne among dermatologic problems, and affect at least three out of four of us at some point in our lives. Warts develop when skin cells are infected by the human papillomavirus (HPV), of which there are more than 70 subtypes. All HPV incorporate their DNA into infected cells, and may remain in our bodies for the rest of our lives. During times of physical or emotional stress, when our immune systems are weakened, viral proliferation can begin and warts appear.
Warts 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 typically appear on the hands, and are caused by eight different subtypes. Other HPV subtypes cause flat warts (usually appearing on the face and legs), genital warts (found in the anogenital areas), and callus-covered plantar warts (on the soles of our feet).
Humans are the only known reservoir of HPV. No other animals, not even toads, are known to carry or transmit the virus. Transmission of HPV occurs primarily through direct contact with infected skin cells. The virus is quite hardy, however, and can survive for considerable periods of time on fomites (inanimate objects such as floors and towels), or in sloughed-off, infected skin cells. Plantar warts, for instance, are thought to be contracted most often from contaminated floors around swimming pools and in communal showers.
The incubation period after inoculation is unknown, but is probably no less than several months. Auto-inoculation 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 and two years can seem a long time! They can bleed if bumped, and they can also seem embarrassing. Treatment of warts seems to decrease the chances that they'll spread.
Common and plantar warts are often effectively treated with over-the-counter remedies. Perhaps the most effective therapy involves covering warts with tiny duct tape bandages. It turns out that some component of duct-tape adhesive is viricidal. The efficacy of duct tape was clearly demonstrated in a study recently published in the New England Journal of Medicine!
Flat warts, facial warts, genital warts, and oral warts are usually treated in a medical office, using a variety of therapies. Ablative treatments include surgical excision, destruction by electrodessication, laser or liquid nitrogen, and chemical "peeling." Topical medical treatments include daily applications of cytotoxic, antiviral, or immunotherapy agents, in the hope of inducing a controlled, localized allergic or immunologic reaction to the infected cells.
Innumerable "alternative" remedies for warts have been tried over the ages, with varying degrees of success. With the important exception of anogenital warts (which can be mutagenic), 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. We have a thermos tank filled with liquid nitrogen, and we're also happy to prescribe the immunotherapy cream Aldara.
Be well! And wear your flip-flops in the showers and locker-rooms!
Jeff Benson, M.D.
Dudley Coe Health Center
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