Around 130 papillomavirus types exist, and each wart shape tends to have its own culprits
Warts are harmless growths caused by the human papillomavirus, which slips in through small breaks in the skin. Most people catch one at some point, and most warts vanish on their own within months or years. Hippocrates was already describing them around 400 BC.
Researchers know of about 130 types of human papillomavirus, or HPV. They infect the flat surface cells of skin and mucous membranes, and each type usually targets only a few parts of the body. That is why warts come in so many forms. Common warts, raised and rough, favour the hands and are mostly linked to types 2 and 4. Plantar warts, or verrucas, form hard and sometimes painful lumps on the pressure points of the soles, often dotted with black specks, and are chiefly type 1. Flat warts are small, smooth and skin-coloured, clustering on the face, neck and hands. Filiform warts grow as thin threads or fingers, often near the eyes and lips, and periungual warts gather like cauliflower around the nails.
Some things raise the odds of infection: public showers and swimming pools, handling meat for a living, eczema and a weakened immune system. Estimates put non-genital warts at somewhere between 1 and 13 percent of the population at any one time, with young people more often affected. Under a microscope a common wart shows thickened outer skin layers, elongated ridges and large blood vessels near the junction with the deeper skin.
Genital warts are usually passed on sexually, and here the virus matters more. HPV types fall into low-risk groups, tied mostly to warts, and high-risk groups tied to cancers, above all of the cervix. Types 6 and 11 account for 90 percent of documented genital wart cases, while types 16 and 18 cause about 70 percent of cervical cancers. Before the HPV vaccine was widely used, about 12 percent of sexually active women were estimated to have genital warts.
The Gardasil vaccine targets all four of those types at once, aiming to prevent both cervical cancer and genital warts. For ordinary skin warts in healthy people, significant problems are uncommon, and options such as salicylic acid or freezing can speed up their disappearance.
Source: Wart
