Genital warts are caused by the Human Papillomavirus, or HPV. There are over 200 types of HPV. Only about 40 types of HPV cause genital warts. The most common types causing genital warts are HPV 6 and HPV 11. Genital warts are almost always sexually transmitted, and several risk factors are involved.

Risk factors for genital warts include:

* Unprotected sex with multiple partners
* Having another sexually transmitted infection
* Starting sexual activity at a young age
* Use of immunosuppressant drugs can increase the risk of genital warts.