Sexually Transmitted InfectionsSexually Transmitted Infections One in five people in the United States had a sexually transmitted infection (STI) on any given day in 2018, totaling nearly 68 million estimated infections. STIs are often asymptomatic (especially in women) and are therefore often undiagnosed and unreported. Untreated STIs can have severe health consequences, including chronic pelvic pain, infertility, miscarriage or newborn death, and increased risk of HIV infection,