How You Get Trichomoniasis

You get trichomoniasis from sexual contact with someone who carries the parasite Trichomonas vaginalis. It passes during penis-to-vagina, vagina-to-penis, or vagina-to-vagina sex when genital fluids and surfaces touch. It lives only in the genital tract, so you can't catch it from toilet seats, towels, saliva, or casual contact CDC.

How trichomoniasis is transmitted

Trichomoniasis is caused by a single-celled protozoan parasite called Trichomonas vaginalis. It's the most common curable non-viral STI in the US, with an estimated 2.6 million infections, and the burden falls heavily on women, who make up more than 80% of cases Sex Transm Dis. The parasite survives in the warm, moist lining of the lower genital tract — the vagina and urethra in women, and the urethra in men. It moves between people when those tissues, and the fluids on them, come into direct contact during sex.

Because the parasite needs that genital-to-genital contact to survive the trip, the transmission routes are specific and limited:

• Penis-to-vagina and vagina-to-penis sex — the most common route, where infected fluids and tissues are in sustained contact long enough for the parasite to take hold in a new host.
• Vagina-to-vagina sex — genital contact between women can pass the parasite even without a penis involved, including by sharing fluids on hands or sex toys that touch both partners' genitals.
• An infected partner with no symptoms — many people who carry T. vaginalis feel nothing at all, so the parasite spreads silently from someone who has no idea they have it.

The parasite can move in either direction during sex — an infected person can pass it on, and an uninfected person can pick it up — which is why both partners are treated even if only one has symptoms. Without treatment, it can stay in the genital tract for a long time, so a recent diagnosis doesn't always mean a recent exposure.

How you do NOT get trichomoniasis

Trichomonas vaginalis can't live on dry surfaces or outside the genital tract for long, so the everyday situations people worry about don't transmit it. You cannot catch trichomoniasis from:

• Toilet seats — the parasite doesn't survive on a hard, cool, dry surface, and ordinary sitting doesn't bring genital tissue into contact with anything infectious.
• Towels, bedding, or clothing — sharing these in normal use doesn't transmit it; the parasite needs living genital tissue, not fabric.
• Swimming pools, hot tubs, or baths — water dilutes and disperses the parasite, and there's no genital contact to pass it.
• Casual contact — hugging, sharing food or drinks, handshakes, or sitting next to someone carries no risk.
• Saliva or kissing alone — the parasite doesn't infect the mouth or throat, so it isn't an oral or respiratory infection.

Put simply, this is a genital infection that needs genital contact. If you've ruled out sexual exposure, you've ruled out the realistic ways to get it.

Who's at higher risk

Anyone who is sexually active can get trichomoniasis, but the risk isn't spread evenly. Women carry the large majority of diagnosed infections, partly because the parasite is easier to detect in the vagina and partly because women are tested more often. Risk climbs with the number of sexual partners and with having a partner who has other untreated STIs or symptoms.

• Women — account for over 80% of US cases and bear most of the symptoms and complications.
• People with a new or multiple partners — more partners means more chances of contact with an undiagnosed carrier.
• People with another STI — trichomoniasis travels alongside other infections and makes catching or passing them, including HIV, more likely.
• Women living with HIV — at higher risk and prone to more persistent infection; the CDC recommends routine annual screening for women with HIV even without symptoms CDC, 2021.

Trichomoniasis in pregnancy

In pregnancy, trichomoniasis isn't just uncomfortable — it raises the chance of preterm birth (delivery before the lungs and other organs are fully ready) and low birth weight, both of which can affect a newborn's health. The infection also increases the risk of acquiring or spreading other STIs, including HIV, by inflaming genital tissue. If you're pregnant and have symptoms or a positive screen, talk with your clinician about trichomoniasis treatment, which is safe to use in pregnancy and clears the parasite.

How to reduce your risk

Because trichomoniasis spreads through genital contact and fluids, the same barrier methods that work for other fluid-borne STIs work here. Two habits do most of the heavy lifting: barrier protection and routine testing.

• Use condoms correctly and every time. Consistent condom use lowers the chance of passing or catching the parasite by keeping infected fluids and tissues from making contact. Partial or occasional use leaves gaps.
• Get tested between partners. Most infections cause no symptoms, so the only way to catch a silent case is to test — routine screening finds what you'd otherwise never notice.
• Treat both partners at the same time. If you're diagnosed, your partner needs treatment too, even with no symptoms, or you'll simply pass it back and forth.
• Don't share sex toys without cleaning or covering them. Fluids on a shared toy can move the parasite between partners.

Condoms used every time lower risk for the sexually transmitted infections, and routine testing catches what has no symptoms — that pairing is the realistic backbone of prevention.

If you think you've been exposed

If a partner tested positive or you had sex without protection with someone whose status you don't know, get checked rather than wait for symptoms — there's a window to keep in mind, so see when to test after exposure for timing, then get tested.

When to see a clinician

See a clinician if you notice unusual genital discharge, itching, burning with urination, discomfort during sex, or genital irritation — and also if a partner has been diagnosed, even if you feel fine. Diagnosis is straightforward; testing usually means a quick swab or urine sample, and the lab looks directly for the parasite or its genetic material. For what the visit involves, see trichomoniasis testing & diagnosis.

Treatment is a course of prescription antibiotics that reliably cures the infection. For women, the 7-day metronidazole course works better than the older single 2-gram dose: in a randomized trial, about 19% of women given the single dose were still infected at follow-up versus 11% on the 7-day course, which is why guidelines now prefer the multi-day course for women Muzny et al.. A diagnosis here is common and treatable — clinics handle it daily, and it says nothing about you as a person. Read more about trichomoniasis treatment & cure.