Genital warts are caused by the human papilloma virus (HPV). There are over 200 subtypes of the virus of which over 25 cause genital infection.
HPV infections of the genital epithelium are thought to be sexually transmitted and are classified as oncogenic (cancer forming or high-risk) (commonly caused by types 16 and 18) and non-oncogenic (low-risk) (commonly caused by types 6 and 11). Infection with the low-risk types is associated with the formation of genital warts.
Cervical cancer is now known to be caused by oncogenic strains of HPV. It is thought that cervical cancer is preceded by the development of high-grade cervical dysplasia, and that cervical cancer can be prevented by removal of these high-grade lesions. People who develop genital warts may acquire an oncogenic strain of HPV at the same time. Low-grade dysplasia may be caused by either an oncogenic or non-oncogenic strain, or both.
The incubation is 2-3 months although it can range from 1-20 months. The period of communicability is probably at least as long as visible lesions persist. Contact infectivity is high if lesions are present but lower if there are no lesions.