Plantar verrucae, or foot warts, are caused by the human papillomavirus (HPV). Plantar warts are contagious and can quickly spread or multiply. Plantar warts often appear on weight-bearing surfaces; however, small breaks in the skin can be an entry point for the virus. The virus thrives in moist, warm environments such as your shoes. Plantar warts are typically treated weekly in our office. Stubborn warts may need to be removed with surgery.