Have unprotected vaginal, anal, or oral sex with someone who has an STI
Share needles or syringes with someone who has an STI
Have direct contact with infected blood, semen, vaginal fluids, or rectal fluids
Have skin-to-skin sexual contact with someone who has a contagious STI, such as herpes, HPV, or syphilis
Pass an STI from parent to baby during pregnancy, childbirth, or breastfeeding
Receive contaminated blood products or organ transplants, which is rare in places with screening
Have sexual contact with multiple partners without testing or protection