One woman said she felt ashamed and disgusted with herself after she tested positive for a high-risk strain of human papillomavirus (HPV). But this sexually transmitted infection (STI) can affect anyone who has ever had a sexual encounter, explains the American Sexual Health Association. In addition, because it may take years for symptoms to develop, it can be difficult to determine when the infection was acquired.

Nearly all cases of cervical cancer can be attributed to infection with the HPV strains 16 and 18, which also cause precancerous cervical lesions.

Because Pap test results may be deceptive, doctors advise that women get both a Pap test and an HPV exam, which determines the presence of any cancerous cells in the cervix. Both exams can be done at a single doctor’s visit. (In men, HPV can lower the quality of semen and cause infertility.)

The good news is that in 2014 the Food and Drug Administration approved Gardasil 9, a vaccine that protects against nine types of HPV, including 16 and 18, and those that cause cancer of the anus, vulva, vagina and penis as well as genital warts, among other conditions.

This is why the Centers for Disease Control and Prevention recommends that all boys and girls get vaccinated at ages 11 or 12. Catch-up vaccines are recommended for males through age 21 and females through age 26 if they didn’t get vaccinated when they were younger.

And here’s some information for older adults: The FDA recently expanded its approval of the vaccine for adults ages 27 through 45.