Trichomoniasis is actually the most common curable sexually transmitted infection, STI, in the world. However, it's thought that many cases are still not recognised and are not diagnosed.
Trichomoniasis is caused by a tiny parasite called Trichomonas vaginalis (TV).
In 2011 just over 6,000 cases were diagnosed in England. In contrast, more than 186,000 cases of Chlamydia were reported the same year. Over 90% of TV cases are diagnosed in women.
However, it's estimated that in the United States of America 7.4 million new cases of TV appear annually compared with 3 million cases of Chlamydia and 718,000 cases of gonorrhoea. Despite being a readily diagnosed and treatable sexually transmitted infection, TV is not a reportable infection and control of it has received relatively little emphasis from public health STI control programmes.
Symptoms of TV usually develop within a month of infection, although up to half of all infected men and women have no symptoms.
The symptoms of TV are similar to those of many other STI's so it can sometimes be difficult to diagnose.
In women, this parasite mainly infects the vagina and urethra (tube that carries urine out of the body). In men, the infection most commonly affects the urethra but the head of the penis or prostate gland (a gland near the bladder that helps produce semen) can become infected too.
TV is usually spread by having unprotected vaginal sex (sex without a condom) or insertion of fingers into the vagina. It could be spread by sharing sex toys, if you don't wash them or cover them with a new condom before use. It can't be caught from oral or anal sex, kissing, hugging, sharing cups, plates, cutlery or from toilet seats.
You don't have to have had many sexual partners to catch TV. Anyone who is sexually active can catch it and pass it on.