Causes of Warts
More than 80 different types of HPV have been identified, and they have tropism (affinity) for different types of body tissue. Most types of HPV have an affinity for the skin and produce common warts (verruca vulgaris), flat warts (verruca plana), and plantar or foot warts (verruca plantaris). Several other types of HPV have an affinity for mucous membranes and some of these cause ano-genital warts (condyloma acuminata).
HPV is passed from person to person by direct or indirect contact, and from one body location to another on the same person. The virus more easily enters the body through an area of skin that is moist, peeling, or cracked.
Some types (e.g., condyloma acuminta) are transmitted sexually. The degree of contact, location of the lesions, the amount of virus present (newer warts tend to contain more viral particles than older warts), and the state of a person's immunity are among the factors that determine HPV infection.