According to the National Cancer Institute at the National Institutes of Health, human papillomaviruses (HPVs) are a group of more than 200 related viruses. More than 40 HPV types can be easily spread through direct sexual contact, from the skin and mucous membranes of infected people to the skin and mucous membranes of their partners. They can be spread by vaginal, anal, and oral sex. Other HPV types are responsible for non-genital warts, which are not sexually transmitted.
Sexually transmitted HPV types fall into two categories: