papovavirus,any of a group of viruses constituting the family Papovaviridae, which is divided into two subfamilies: the papillomaviruses and the polyomaviruses. Papovaviruses are responsible for a variety of abnormal growths in animals: warts (papillomas) in humans, dogs, and other animals; tumours (polyomas) in mice; and vacuoles (open areas) in cells of monkeys. The virus particle lacks an outer membrane; is spheroidal, about 45 nanometres (nm; 1 nm = 10 - 9 metre) across; is covered with 42 subunits called capsomeres; and contains deoxyribonucleic acid (DNA). Papovaviruses develop in the nuclei of cells, in which they can be seen in apparent crystalline arrangements.