Trichomoniasis is a sexually transmitted disease (STD) caused by a parasite that is passed from one person to another through sexual contact or through close contact with damp objects that contain the parasite. Also known as “trich” or “trick,” it infects both sexes, but is more common in women. It is the most common, curable STD in young women, and infects 7.4 million women and men every year, according to the U.S. Centers for Disease Control and Prevention (CDC).

In the United States, about 5 to 10 percent of all women are infected with trichomoniasis, according to the National Women’s Health Resource Center. In addition, some studies have found that up to 50 percent of women infected with other STDs also are infected with trichomoniasis. Rates are much higher for African-American women than for white and Hispanic/Latina women.

A single-celled protozoan parasite called Trichomonas vaginalis causes trichomoniasis.

Women can become infected through penis-to-vagina or vulva-to-vulva contact. Infection can also be spread through oral or anal sex. In addition, a woman can become infected if her genitals come into contact with certain objects that are infested with the parasite. These objects include:

• Damp towels and washcloths
• Wet clothing, such as bathing suits
• Toilet seats

Trichomoniasis is considered one of the three main types of vaginitis. Many women with trich do not feel the symptoms of vaginitis (e.g., burning sensation, discomfort with urination).

Although people with trichomoniasis often experience no symptoms of infection, they can still pass the disease on to others. Trichomoniasis infection makes a person more vulnerable to other STDs, including the human immunodeficiency virus (HIV), which can cause acquired immune deficiency syndrome (AIDS). This is because infection with trichomoniasis stimulates the immune system, resulting in higher production of the immune response cells that the HIV virus targets. In addition, women who have both HIV and trichomoniasis are more likely to infect their partners with the HIV virus.

Pregnant women who are infected with trichomoniasis may experience premature rupture of membranes (PROM), premature labor and delivery, and may give birth to babies who have low birth weight (less than 5 pounds, 8 ounces, or 2,500 grams). For this reason, it is important for pregnant women to inform their obstetrician-gynecologist (ObGyn) if they are experiencing symptoms of the condition.