Warts are caused by viruses, called human papillomaviruses (HPV). Most papillomaviruses, like the ones that cause common skin warts (verruccae vulgaris), are benign. Warts almost always go away by themselves because the body's immune system eventually recognizes the infected tissue, mounts an attack and rejects them, leaving clear skin and no trace of the wart.
But all papillomaviruses are not the same and the diseases they cause don't always go away by themselves. Of the hundred or so papillomaviruses that cause infections in humans, several cause venereal warts (condyloma accuminatum) and some can even cause cancer. Human papillomavirus-16 is the cause of about 50% of cervical cancers.
Cancer of the cervix is diagnosed in 16,000 North American women every year causing over 5,000 deaths annually on this continent and over 450,000 globally. These numbers were higher in the mid-twentieth century before routine screening using Papinocolaou smears or Pap tests was initiated, mainly in the western world. Cervical cancer remains more common in third world countries. It is a disease associated with sexual activity. The younger a woman is when she becomes sexually active, as well as the greater the number of sex partners and pregnancies she has had, the greater her risk of cervical cancer.
Other risk factors include smoking, use of oral contraceptives rather than barrier methods, and low socioeconomic status. The male sex partner serves as the vector for transmitting the virus, so sex with a male who had a previous partner with papillomavirus infection results in increased risk for papillomavirus infection and cervical cancer. There is an increased susceptibility to papillomavirus infection during pregnancy, if someone is immunocompromised with diabetes or HIV infection or after local trauma to the genital area.
The majority of women diagnosed with cancer of the cervix have not had a Pap test performed for several years.
A study reported in the November 20, 2002 New England Journal of Medicine reported promising research on a vaccine to prevent papillomavirus-16 infection. Merck Pharmaceuticals sponsored a clinical trial by Dr. Laura Koutsky of the University of Washington to test a new vaccine. The vaccine was developed by creating a synthetic protein with similar molecular structure to the outer coat of the papillomavirus-16. When the body detects a foreign protein, it manufactures cells and antibodies to attack and remove it. In the study, 1,200 sexually active women treated with 3 injections of the experimental vaccine were compared to 1,200 women who were given placebo. 18 months after the treatment, when the 2 groups were compared, papillomavirus-16 infection was detected in 41 of the controls but in none of the women who received the vaccine. Further research is needed and the next step will be to develop a vaccine that will prevent infection with the other strains of papillomavirus that cause cervical cancer.
The real challenge, common to all areas of medical advances, will not only be to develop the newer, more effective technologies, but to effectively distribute them to the populations in greatest need.
A final word about Pap tests: Pap tests have proven themselves as one of the most effective methods of cancer prevention in women, so if you are a woman who has had one or more sexual partners, make sure you get regular pap tests.
Ray Baker, MD