Genital warts and genital papillomavirus disease

Genital infection with human papillomavirus (HPV) is a common STI. Reliable estimates indicate a lifetime risk of infection of more than 50% for the population. Genital HPV infection can be divided into infection with genotypes less likely to be associated with neoplasia (low oncogenic risk) and genotypes with a stronger association with neoplasia (high oncogenic risk). A family of high-risk HPVs has been described, including HPV types 16, 18, 31, 33, 35, 39 and 45. Most high-risk HPV infections are asymptomatic and resolve spontaneously within 1 year. Persistent infection with high-risk HPV causes epithelial dysplasia. This can progress to invasion, and high-risk HPV has been shown to be a necessary cause of cervical cancer; HPV 16 alone causes more than 50% of cases. High-risk HPV is also causative in 90% of anal and vaginal squamous carcinomas, and 40% of vulval and penile cancers. Low-risk HPV infection usually manifests as anogenital warts, caused by HPV types 6 and 11. This is the most common clinically recognized viral STI. Treatments for genital warts can be divided into self-treatments such as podophyllotoxin and imiquimod, and clinic-based treatments such as cryotherapy, trichloroacetic acid and electrosurgery. Recurrence of genital warts after apparent cure is common. Prophylactic HPV vaccines using virus-like particles are under development; phase II trials have shown 90-100% efficacy against persistent infection and disease, and the results of ongoing phase III trials are awaited.