HPV usually has no signs or symptoms and can infect both men and women. Although most sexually active people will get it at some point in their lives, they may never know it without regular checkups, including someone with one regular sexual partner. The immune system usually clears HPV up within two years, but for some people it never goes away. High-risk HPV seldom causes genital warts, but for men, that's the only way they'll know (outside of an exam) because there's no clinically validated test for men with HPV. Females, on the other hand, can find out through regular pap smears and by asking to be tested for HPV. Abnormal cells may show up, and if necessary, a colposcopy can be done to find out whether she has HPV or not. For women under age 26, the HPV vaccine is recommended even for those who already have it. There's a vaccine for guys to prevent genital warts.