Trichomoniasis: The Most Common Curable STI You’ve Never Heard Of

Key Takeaways:

• Trichomoniasis is caused by Trichomonas vaginalis, a single-celled parasite—the most common curable nonviral STI worldwide.
• Women often develop frothy, yellow-green discharge with odor and itching; up to 70% of infected people show no symptoms.
• Untreated, it raises the risk of other STI acquisition and complicates pregnancy with preterm birth risk.
• One dose of prescription antibiotics cures it—partners must be treated simultaneously to prevent reinfection.

What It Is & How It Spreads

Trichomoniasis—'trich'—is caused by the parasite Trichomonas vaginalis, and the CDC estimates roughly 3.7 million Americans carry it at any time. It spreads through genital contact during sex, and condoms reduce but do not eliminate transmission, since the parasite can live on nearby skin. Women are more often diagnosed; men frequently carry it without symptoms, which quietly sustains transmission chains.

Symptoms usually appear 5–28 days after exposure. In women: frothy yellow-green vaginal discharge, a strong 'fishy' odor, vulvar itching, discomfort during urination or sex, and occasionally spotting. In men: transient urethral irritation or discharge, mild burning with urination. Most infections—especially in men—are asymptomatic, so screening history matters more than symptoms.

Testing, Cure & Partner Treatment

Diagnosis uses nucleic acid amplification tests (NAAT) or a clinic swab—home STI panels increasingly include trich alongside chlamydia and gonorrhea. Treatment is straightforward: a single oral dose of metronidazole or tinidazole clears the infection in the vast majority of cases, with nitroimidazole regimens reserved for stubborn cases.

• Abstain from sex until both you and your partners have finished treatment—typically 7 days after single-dose therapy.
• Treat every sex partner from the past month simultaneously, even if they feel fine.
• Retest at 3 months to confirm cure and check for other STIs.
• Complete pregnancy testing before metronidazole if there is any chance of conception, and review timing with your clinician.

Because trich increases susceptibility to HIV and other infections and raises preterm-birth risk in pregnancy, clearing it is not optional maintenance—it is prevention for the whole sexual-health picture. If your STI panel was drawn without trich, ask for it explicitly; routine inclusion is a growing best practice.

Medical Disclaimer: Reviewed by the Amble Clinical Editorial Team. This guide is for educational purposes and does not replace individualized medical advice from a licensed clinician.