Verrucas on foot. Close-up of the sole of a foot showing several verrucas. A verruca (or plantar wart) is a rough area on the foot caused by a papillomavirus. They are the same as other warts, but the pressure on the sole of the foot causes them to flatten into the skin. They are commonly caught from floors in wet communal areas such as swimming pool changing rooms and group showers. A verruca can quickly spread to other areas of the foot, as seen here. The large verruca has smaller companions at upper left and far left. They can be removed by cryosurgery (freezing them off the foot), cutting out the infected area, or applying salicylic acid plasters.