HPV is a common virus transmitted sexually; by age 27, most sexually active individuals have been exposed unknowingly. Doctors rarely identify specific strains. Certain types, like strains 6, 11, 16, and 18, can cause genital warts. HPV strains 16, 18, and others pose risks like cancer of the cervix, vulva, vagina, penis, anus, and head/neck (tongue, tonsils, throat)..