What are the causes of genital warts?

HPV types 6 and 11 are the dominant causes of genital warts. These types are not associated with cancer of the vulva, anus, cervix or penis. HPV 16 and 18 are independent infections associated with cervical cancer.

HPV is transmitted through skin-to-skin contact, usually during sexual intercourse. During intercourse the virus can enter cells of the skin or mucosal layers of the genital tract through small breaks and multiply there. It may remain dormant or multiply further, causing a wart. The wart is possibly most contagious, but the virus in invisible lesions (subclinical lesions) can also be transmitted. This makes it difficult to prevent the spread of genital warts.

Condoms provide a mechanical barrier if they are used correctly, but the virus can also be located on the scrotum or the vulva, and infect the other partner during sex.

Although the virus can be transmitted during birth, this type of transmission is very rare (about 0.05% of individuals with HPV infection will deliver an infant with vocal cord infection by the virus). There is evidence that children acquire papillomavirus infections of many varieties long before they become sexually active; the routes of infection in children are not understood at this time.

Who gets it?

All individuals who engage in sexual activity (that is nearly every human being) are at risk of acquiring HPV infection. It is without doubt the most common sexually transmitted infection in the world. Since the virus is transmitted through skin-to-skin contact, it is important to note that penetration is not essential for the transmission of the virus between individuals. Genital to genital contact is sufficient to enable transmission of the virus. The infection rate of HPV in South Africa is unknown, but it is estimated that about 100 000 to 200 000 new cases are found every year. Infection rates of 5% to 10% are common among young adults. Sophisticated analysis finds HPV DNA (genetic material) in the cells of 25% to 50% of all patients attending gynaecology clinics.

Risk factors

Sexual activity with multiple partners and without protection from condoms massively increases the risk of any sexually transmitted disease, and genital warts are no exception.

Those with decreased immune system function are more susceptible to this infection and the warts may enlarge rapidly during pregnancy.

(Reviewed by Professor Lynette Denny, Gynaecology Oncology Unit, Department Obstetrics & Gynaecology, University of Cape Town/Groote Schuur Hospital, August 2008)


Thank you for participating