Plantar warts are benign epithelial tumors caused by infection by human papilloma virus types 1, 2, 4, or 63. All warts can spread from one part of your own body to another. They may spread from one person to another, but this is uncommon. Infection typically occurs on moist walking surfaces such as showers, swimming pools, or shoes. The virus can survive many months without a host, making it highly contagious.