The parasite passes from an infected person to an uninfected person during sex. In women, the most commonly infected part of the body is the lower genital tract (vulva, vagina, cervix, or urethra). In men, the most commonly infected body part is the inside of the penis (urethra). During sex, the parasite usually spreads from a penis to a vagina, or from a vagina to a penis. It can also spread from a vagina to another vagina. It is not common for the parasite to infect other body parts, like the hands, mouth, or anus. It is unclear why some people with the infection get symptoms while others do not. It probably depends on factors like a person’s age and overall health. Infected people without symptoms can still pass the infection on to others.
Trichomoniasis is a sexually transmitted infection (STI) caused by a parasite. The parasite is spread most often through vaginal, oral, or anal sex. It is one of the most common STIs in the United States and affects more women than men. It is easily treated with antibiotics, but many women do not have symptoms. If left untreated, trichomoniasis can raise your risk of getting HIV.

The advent of new, highly specific and sensitive trichomoniasis tests present opportunities for new screening protocols for both men and women.[24][27] Careful planning, discussion, and research are required to determine the cost-efficiency and most beneficial use of these new tests for the diagnosis and treatment of trichomoniasis in the U.S., which can lead to better prevention efforts.[24][27]