"Many cases of chlamydia, gonorrhea, and syphilis continue to go undiagnosed and unreported, and data on several additional STDs—such as human papillomavirus, herpes simplex virus, and trichomoniasis—are not routinely reported to the CDC. As a result, the annual surveillance report captures only a fraction of the true burden of STDs in America. The CDC estimates that nearly 20 million new sexually transmitted infections occur every year in the United States, half among young people aged 15–24, and account for almost $16 billion in health care costs. Each of these infections is a potential threat to an individual’s immediate and long-term health and well-being. In addition to increasing a person’s risk for acquiring and transmitting HIV infection, STDs can lead to chronic pain and severe reproductive health complications, such as infertility and ectopic pregnancy. Bacterial vaginosis is a common, possibly sexually transmitted, vaginal infection in women of reproductive age. It occurs when problematic bacteria that are normally present only in small amounts increase in number, replace normal vaginal lactobacilli bacteria, and upset the usual balance. The most common sign is a thin, milky discharge that is often described as having a fishy odor, although some women have no symptoms. Having bacterial vaginosis increases the risk of getting other STDs/STIs and is also associated with pelvic inflammatory disease, postoperative infections, and possibly preterm labor and birth. Trichomoniasis is caused by the single-celled protozoan parasite Trichomonas vaginalis and is common in young, sexually active women. The parasite also infects men, though less frequently, and can be transmitted between men and women as well as between women whenever physical contact occurs between the genital areas. Infections do not always cause symptoms, but they can cause frequent, painful, or burning urination in men and women, as well as vaginal discharge, genital soreness, redness, or itching in women. Because the infection can occur without symptoms, a person may be unaware that he or she is infected and continue to re-infect a sexual partner. All sexual partners should be treated at the same time to avoid re-infection. During pregnancy, Trichomonas infection is associated with an increased risk of premature birth and infants with low birth weight. Infants born to mothers with Trichomonas infection are more than twice as likely as infants born to uninfected women to be stillborn."