Medical Disorders Network

Although sexually transmitted, human papillomavirus—the cause of genital warts—is not a disease that doctors must report to the Centers for Disease Control and Prevention, it is believed, on the basis of epidemiological studies, that there are about 500,000 to 1 million new cases every year. More than 100 types of human papillomavirus (HPV) have been identified in humans, and researchers expect the final number to be around 200.


Causes

External genital warts (EGWs) are most often caused by human papillomavirus type 6 (HPV-6) and sometimes by HPV-11, both of which researchers rate as low-risk in that these are not the types that typically lead to cervical cancer. Skin-to-skin contact with productive lesions that are shedding HPV DNA is the number-one means of transmission of HPV. Thus, genital sexual contact is the cause of HPV.

Condoms give some protection, but their overall efficacy in curbing transmission rates is dubious. HPV can be contracted from parts of the penis and groin that are not covered by condoms. Furthermore, HPV transmission appears to take place even when there are no visible lesions: human papillomavirus DNA has been detected during asymptomatic infection stages.

Genital warts (condylomata acuminata or venereal warts) are caused by certain types of HPV, whereas other HPV infections tend to cause warts on the hands and soles of the feet but not genital warts. It is rare (but possible) for genital warts to be transmitted by fomites (any nonliving material such as surgical gloves) and by infectedmothers to newborns.

Incubation period for EGWs is about one month to two years, and in most cases, the infected individual has warts within a few months of exposure to HPV. Left untreated, these can regress, remain the same, or get larger. In people with clinical HPV infection that manifests itself in external genital warts, about 20 percent of lesions actually resolve spontaneously—typically, within the year that they first became apparent.

It has been observed that HIV/AIDS patients, transplant recipients, and others with suppressed immune systems experience florid warts and have high rates of recurrences after treatment, suggesting that a key player in containment of HPV is cell-mediated immunity.

HPVs, members of the papovavirus family, can live in a human being dormantly for months or years and then, if the person’s immune system becomes weak, respond by activating and replicating. Anogenital HPV has far-reaching effects: 24 to 40 million people are affected in the United States, and each year, about 1 million more new cases are diagnosed. Of all people in the United States who are sexually active, about 2 percent have genital warts that are clinically visible. Many more show signs of infection that is subclinical.