Even if a person has never had any sexual contact, it is possible that they may have been exposed to an STD. Many individuals acquire oral herpes through casual affection with their family members. Other people are exposed to their mothers' STDs during pregnancy or birth. It is also possible to become infected with diseases, such as HIV, through nonsexual risk behaviors, such as injection drug use.
Although relative sexual inexperience does make it less likely that a person will have an STD, don't assume that just because someone says they're a virgin that you are not taking a risk. It's still important to practice safe sex, if for no other reason than it's a good life-saving habit. Furthermore, what about putting your partner at risk? Contrary to some popular myths, people can get pregnant the first time they have sex, and sleeping with a virgin won't cure your HIV or other STDs.
When it comes to sex, it's better to be safe than sorry.