There are over 100 different types of human papillomavirus (HPV), which infect different parts of the body. Around 50 types can infect the genital skin, including the cervix.
Infection with HPV is so common it can be considered a normal part of being sexually active.
Four out of five people who have ever had sex will have HPV at some point in their lives. In most of us the infection is invisible, harmless and transient - that is, it goes away after a few months without causing any problems.
Occasionally, some types of HPV persist in the body. We don't really know why this happens in some people and not others, although some factors (like smoking) seem to make it happen more easily.
Condoms may offer some protection from infection with HPV, but this is limited as they do not cover all the genital skin.
Lucy's story
I've always been very aware of the importance of regular Pap tests, as my Mum had early-stage cervical cancer in her 30s.
She encouraged me to start having regular Pap tests when I turned 18 and I followed her advice, albeit begrudgingly!