Papillomaviruses and polyomaviruses

There are nearly 200 human papillomavirus types that infect epithelia of skin and mucous membranes. They infect only humans, and cause conditions including the following: skin warts and verrucas, which are caused by types 1 and 2; infection initiated when, after minor skin abrasions, for example, the basal cells of the epithelium come in contact with infectious virus; anogenital warts, which are caused by types 6 and 11; transmitted by direct sexual contact, these are the most common sexually transmitted infection; present clinically as multiple exophytic lesions or as subclinical flat lesions. They can be treated topically with podophyllin or imiquimod, or by ablative surgical methods. Recurrences are common. A highly efficacious prophylactic vaccine is available.