Use a comma to separate nonessential elements from a sentence. More specifically, when a sentence includes information that is not crucial to the message or intent of the sentence, enclose it in or separate it by commas.
Genital warts are a sexually transmitted infection (STI) caused by certain strains of the human papillomavirus (HPV). These skin growths can cause pain, discomfort, and itching. They are especially dangerous for women because some types of HPV can also cause cancer of the cervix and vulva.
Genital warts are caused by low-risk types of human papillomavirus (HPV). These viruses may not cause warts in everyone. Women can get genital warts from sexual contact with someone who has HPV. Genital warts are spread by skin-to-skin contact, usually from contact with the warts. It can be spread by vaginal, anal, oral, or handgenital sexual contact. Genital warts will spread HPV while visible, and after recent treatment.