Although not widely known, trichomoniasis is a common STI that affects 7.4 million men and women every year. Trichomoniasis is caused by the single-celled protozoan parasite, Trichomonas vaginalis, and is more likely to infect woman than men. The parasite affects the vagina in women and the urethra in men. It is sexually transmitted through penis-to-vagina intercourse or vulva-to-vulva contact with an infected partner; woman are able to contract the parasite through both heterosexual and homosexual contact while men can usually only become infected through heterosexual intercourse. Men are often asymptomatic, but when symptoms do occur they have an irritation inside the penis, a slight/mild discharge and burning after ejaculation and urination. Symptoms in women may include yellow-green vaginal discharge with a strong intercourse, discomfort during intercourse and urination, and irritation and itching of genital area. The inflammation caused by the infection may also increase the risk of a woman contracting HIV if she is expose to the virus, as well as increasing the probability that a woman infected with HIV will pass the virus to her sex partners. Trichomoniasis is diagnosed by a health care provider, although infection is harder to detect in men than in women. Trichomoniasis can be cured with prescription drugs that are taken orally in a single dose. These drugs, however, only cure the one infection and do not make a person less susceptible to contracting the parasite in the future.