Genital warts are caused by the human papilloma virus (HPV).

HPV is not a single virus, but a family of more than 100 different strains of viruses. However, most cases of genital warts are caused by two strains of the virus – type 6 and type 11.

Most cases of HPV infection do not have visible symptoms, so many people can be infected with HPV without realising.

It is still possible to pass on genital warts if they are not currently visible.

HPV transmission

The most common way HPV can be passed from person to person is through skin to skin contact. This is usually sexual activity such as:

• vaginal sex
• anal sex
• non-penetrative genital to genital contact
• sharing sex toys
• in very rare cases, oral sex

HPV is not passed on through kissing, hugging or sharing towels, clothing and everyday items such as cutlery or a toilet seat.

A condom can help protect against genital warts. However, as it does not cover all of the genital area, it may still be possible to pass HPV on to uncovered areas of skin.

In rare cases, a mother can pass HPV on to her newborn baby during birth.

In very rare cases, someone with HPV warts on their hands could pass on an infection by touching somebody else's genitals.