Transmission of HPV through routes other than sexual is definitely possible. One may be exposed to HPV simply by shaking hands as suggested in the finding of HPV virus under fingernails.
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.
Am J Epidemiol 2003 Feb 1;157(3):218-26:
Genital human papillomavirus infection: incidence and risk factors in a cohort of female university students.
Winer RL, Lee SK, Hughes JP, Adam DE, Kiviat NB, Koutsky LA. Department of Epidemiology, University of Washington, Seattle, WA 98103, USA.
“Incidence data on human papillomavirus (HPV) infection are limited, and risk factors for transmission are largely unknown. The authors followed 603 female university students in Washington State at 4-month intervals between 1990 and 2000. At each visit, a sexual and health questionnaire was completed and cervical and vulvovaginal samples were collected to detect HPV DNA. At 24 months, the cumulative incidence of first-time infection was 32.3% (95% confidence interval: 28.0, 37.1). Incidences calculated from time of new-partner acquisition were comparable for enrolled virgins and nonvirgins. Smoking, oral contraceptive use, and report of a new male sex partner––in particular, one known for less than 8 months before sex occurred or one reporting other partners––were predictive of incident infection.
Always using male condoms with a new partner was not protective. Infection in virgins was rare, but any type of nonpenetrative sexual contact was associated with an increased risk. Detection of oral HPV was rare and was not associated with oral-penile contact. The data show that the incidence of HPV associated with acquisition of a new sex partner is high and that nonpenetrative sexual contact is a plausible route of transmission in virgins.”