Papillomaviridae is an ancient
taxonomic family of non-
enveloped DNA viruses, collectively known as
papillomaviruses. Several hundred species of papillomaviruses, traditionally referred to as "types", have been identified infecting all carefully inspected mammals, but also other
amniotes such as birds, snakes and turtles. Infection by most papillomavirus types, depending on the type, is either asymptomatic (e.g. most Beta-PVs) or causes small benign tumors, known as
papillomas or
warts (e.g.
human papillomavirus1, HPV6 or HPV11). Papillomas caused by some types, however, such as
human papillomaviruses 16 and 18, carry a risk of
becoming cancerous.