HPV is the most prevalent sexually transmitted infection in the world. It is estimated that as many as 40 million Americans are infected with HPV, and the incidence of this disease appears to be increasing. And, unlike other STDs such as gonorrhea or HIV/AIDS, use of condoms and other safe-sex practices may not be nearly as effective in preventing infection. This is because the papillomavirus lives in the skin cells covering the pubic area (vulva and shaft of the penis) as well as the interior cells lining the vagina and cervix in women, and urethra and anus in both sexes.
Condoms do not cover the entire shaft of the penis nor do they block contact with pubic skin. Therefore, during intercourse, even with a condom, skin cells containing HPV can come in contact with a woman's vulva or vagina, enabling the virus ultimately to reach the cervix. In addition, the friction of sexual intercourse is believed to cause tiny, microscopic tears in the vaginal wall, making transmission far more likely. Moreover, even dead cells shed during intercourse can contain the virus and remain infective for days (Information credited to Roden, Lowy and Schiller, 1997).
http://www.reproline.jhu.edu/english/3cc/3refman/cxca_hpv2.htm
Transmission of HPV through routes other than sexual is definitely possible. One may be exposed by something as innocent as shaking hands with someone as proven in Sexually Transmitted Infections 1999 Oct;75(5):317-9. Detection of human papillomavirus DNA on the fingers of patients with genital warts. Sonnex C, Strauss S, Gray JJ, Department of GU Medicine, Addenbrooke's Hospital, Cambridge, England: "14 men and eight women with genital warts had cytobrush samples taken from genital lesions, finger tips, and tips of finger nails. Samples were examined for the presence of HPV DNA by the polymerase chain reaction.
HPV DNA was detected in all female genital samples and in 13/14 male genital samples. HPV DNA was detected in the finger brush samples of three women and nine men. The same HPV type was identified in genital and hand samples in one woman and five men. This study has identified hand carriage of genital HPV types in patients with genital warts. Although sexual intercourse is considered the usual mode of transmitting genital HPV infection, our findings raise the possibility of transmission by finger-genital contact."
Condoms offer little protection against HPV since any skin-to-skin contact can result in transmission of the virus.
