HUMAN PAPILLOMAVIRUS (HPV) – OVERVIEW

Human papillomaviruses (HPV) are extremely common DNA viruses that only infect humans. HPV infect epithelial cells. Infection with low-risk HPV types causes external genital warts. Persistent infection with high-risk HPV types causes virtually all cancers of the cervix and a significant proportion of cancers of the anus, oropharynx, vagina, vulva and penis. There are more than 100 types of HPV, which may be subdivided into either cutaneous or mucosal categories depending on their tissue preference. There are more than 40 types which infect the anogenital and oropharyngeal mucosa. These can be broadly split into “high-risk” and “low-risk” types based on their association with the development of malignancy.

• Low-risk HPV (lrHPV) – HPV 6 and HPV 11 cause approximately 90% of genital warts and are only rarely associated with precancer or cancer of the lower genital tract.
• High-risk HPV (hrHPV) – The 14 most oncogenic HPV types include types 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 66 and 68. Types 16 and 18 are most commonly associated with development of cancer, together accounting for about 70% of invasive cervical cancers. However, not all infections with HPV 16 or 18 progress to cancer. In addition, HPV 16 is strongly associated with anal and throat cancer.

Clinical presentations

• Genital warts (condyloma acuminata). HPV infects the penis, scrotum, perineum, anal canal, perianal skin, vaginal introitus, vulva, cervix.
• Squamous intraepithelial lesions (SILs) of the vagina, cervix, anus, penis. HPV infection has been clearly linked to nearly all SILs and cancers of the cervix and anus. HPV is also linked to a subset of penile, vulval and vaginal cancer.
• Oropharyngeal cancer (see HPV-related Disease in the Head and Neck).
• Infection of respiratory mucosa also occurs, particularly but not exclusively in children.

Subclinical HPV infection

• Subclinical means not visible to the naked eye. May be hrHPV and/or lrHPV.
• Subclinical HPV infection is most commonly detected by cervical cytology or biopsy specimens.
• HPV DNA testing is currently available only as an adjunct to cervical cytology. HPV DNA testing has no clinical utility in sexually transmitted infection (STI) screening. hrHPV testing has been shown to be effective as a primary screening test to reduce cervical cancer rates for both unvaccinated and vaccinated women.(1) The NCSP is in the process of redeveloping the programme towards primary screening with the HPV test, in line with a number of other international cervical screening programmes. Vaccination is the first line of prevention and regular screening with hrHPV testing is the second line of prevention. There are no screening tests clinically available for HPV detection from oropharyngeal, anal, or male genital specimens. Neither are there any approved serologic or blood tests.