Wart virus. Coloured transmission electron microg- raph of a single Papilloma virus. This icosahedral-shaped DNA virus (green at centre) has a coat containing 72 capsomers (protein units). Papilloma virus (human papillomavirus or HPV) is the cause of warts: these commonly grow on hands and soles of the feet, on mucous membranes of the body and on the genitals. Papilloma viruses belong to the papovavirus group of which most members are capable of inducing non-malignant tumours. HPV virus has been implicated in certain skin and cervical cancers. Magnification: unknown.