Trichomoniasis, commonly called “trich” (pronounced “trick”), is a very prevalent sexually transmitted disease that’s caused by a parasitic infection. While trich often causes no symptoms, it can be irritating and uncomfortable, and untreated trich can raise a person’s risk of contracting or spreading other sexually transmitted diseases (STDs).

Untreated infections can last months or even years, which for many people impacts not only their physical health but also their sex life, as trich can cause discharge from the genitals as well as make sex feel painful instead of pleasurable.

An estimated 180 million cases of trich occur worldwide each year, and prevalence in the U.S. is estimated at up to 5 million cases per year, but because most cases go undiagnosed, little is known about exactly how often this infection occurs in the population.

To understand more about this common (and easily treated) STD, let’s look at all the available data and information behind trich.

What Is Trich?

A protozoan parasite called Trichomonas vaginalis causes trich infections, passing from person to person during sex. Trich is carried through bodily fluids that are readily exchanged during sex, including semen, vaginal fluids and pre-cum.

Trich spreads most commonly through vaginal sex, though it also can be transmitted by sharing sex toys, touching vulvas or touching yours or your partner’s genitals with a hand that has infected fluids on it. Though it’s rare, trich can infect the mouth or the anus as well, but it does not spread through non-sexual contact like hugging or holding hands.

More than 8 in 10 women who were diagnosed with trich reported experiencing no symptoms of the infection, though when symptoms do appear, the most common is vaginitis, or irritation of the vagina or vulva. Other symptoms, some of which can appear in both men and women, include:

  • Discharge from the penis or vagina that can be frothy or foul-smelling
  • Frequent urination
  • Burning sensation or pain when peeing
  • Spotting or irregular periods

Trich is a very easily treated infection and for most people can be cleared up with just a single dose of antibiotics, usually either tinidazole or metronidazole. Trich is very easily contracted, so even if you’ve had it before, it’s possible to get it again through re-exposure to the bodily fluids of an infected person.

Who Is Most Likely to Have Trich?

While anybody who is sexually active could potentially contract or spread trich, the disease is most common in women and people who have sex with women. Of the estimated 5 million infections that occur in the U.S. every year, it’s believed that most involve people between 15 and 24 years of age.

In addition to new infections impacting young people more than other age groups, research has found that trich is more common among black women than women in other ethnic groups.

Prevalence by ethnicity

African-American 13.30%
Hispanic/Latino 1.80%
White 1.30%

Trich was far more common in decades past, so older women may actually be more likely to have trich than younger women based on the general presence of the infection, though most new cases are reported in those between 15 and 24.

Trich Over Time

CDC data suggest that trich is much less common today than it was in the 1960s and 1970s, possibly owing to increased use of condoms. According to information contained in reports of womens’ initial visits to doctors’ offices for STDs and complications, the number of diagnoses of trich is less than half what it was in 1966, the first year for which data is available.

Trich infections by year

1966 579,000
1967 515,000
1968 463,000
1969 421,000
1970 529,000
1971 484,000
1972 574,000
1973 466,000
1974 427,000
1975 500,000
1976 473,000
1977 324,000
1978 329,000
1979 363,000
1980 358,000
1981 369,000
1982 268,000
1983 424,000
1984 381,000
1985 291,000
1986 338,000
1987 293,000
1988 191,000
1989 165,000
1990 213,000
1991 198,000
1992 182,000
1993 207,000
1994 199,000
1995 141,000
1996 245,000
1997 176,000
1998 164,000
1999 171,000
2000 222,000
2001 210,000
2002 150,000
2003 179,000
2004 221,000
2005 165,000
2006 200,000
2007 205,000
2008 204,000
2009 216,000
2010 149,000
2011 168,000
2012 219,000
2013 225,000
2014 155,000
2015 139,000
2016 222,000

Though the number of cases reported by physicians in 2016 is well under half the number reported 50 years earlier, that figure could represent a disturbing trend. Between 2015 and 2016, doctor visits for trich rose by nearly 60%. Plus, we know that trich is notoriously difficult to diagnose because most people do not have symptoms.


The data on how common trich is isn’t exactly full, but the picture that can be painted with the limited data available indicates that trich is less common that it was in decades past but that because the STD spreads so easily and rarely causes those infected to display symptoms, individuals who are at risk of contracting trich should still be quite concerned.

According to the CDC, about 2.3 million women 14-49 become infected with trich every year, but only 222,000 women sought treatment for trich from their doctors, which indicates that most people who have trich don’t get treatment.

Everyone who is at risk of trich should get tested to ensure they are able to remove the infection from their bodies and avoid passing the STD along to their sexual partners.

Additional References

Centers for Disease Control and Prevention, Sexually Transmitted Diseases, Trichomoniasis Statistics. (2017). Retrieved from

The Prevalence of Trichomonas vaginalis Infection among Reproductive-Age Women in the United States, 2001–2004, Clinical Infectious Diseases. (2007). Retrieved from

Centers for Disease Control and Prevention, Sexually Transmitted Disease Surveillance 2017, Table 44. Selected STDs and Complications — Initial Visits to Physicians' Offices, National Disease and Therapeutic Index (NDTI), United States, 1966–2016. (2017). Retrieved from

Centers for Disease Control and Prevention, Trichomoniasis CDC Fact Sheet. (Undated). Retrieved from