Plantar warts arise from direct contact with a strain of human papillomavirus (HPV). You may recognize HPV as the virus commonly associated with cervical cancer and genital warts. However, there are more than 100 types of HPV, some of which can cause plantar warts.
The virus enters the blood stream through breaks in the skin. In many cases, antibodies kill the virus on contact, but if this doesn't occur, warts can form on the weight-bearing parts of the feet. A plantar wart forms when the virus causes skin cells in the foot to multiply quickly, creating a thick, excess growth of skin [source: PDRhealth]. The virus may incubate between one to 20 months, so it can be hard to pinpoint the time or source of the infection [source: Cooper].
HPV thrives in warm, moist environments. Spaces such as shower floors, locker rooms and pools are all hospitable environments for the virus, so the mere act of walking on these surfaces with bare feet can cause plantar warts.
Once a plantar wart has developed, it can spread in several ways. Untreated plantar warts can spread on their own into wart clusters or grow to an inch (2.54 centimeters) or more in circumference. A person with plantar warts also can spread them to other areas of the foot by scratching or touching the wart. In addition, contact with any skin or blood shed from the wart may cause other warts to develop [source: Mayo Clinic].
Now that you know a virus causes plantar warts, you may be wondering if you can catch plantar warts from someone else. Read on to the next page for the answer.