Doctors in New York are describing the first known U.S. cases of sexually transmitted ringworm, which can cause a nasty rash that can take months to get under control.

Despite the name, ringworm is not just any kind of worm, but a fungus, Trichophyton mentagrophytes. It is more commonly known as jock itch (when it affects the groin area) or athlete’s foot and can produce a round, itchy rash.

Until now, transmission of the fungal infection through skin-to-skin sexual contact has been rare, although cases have been reported in Southeast Asia and France since 2021, the researchers reported. These were a subtype of T. mentagrophytes called TMVII.

The new report concludes that the first US case of sexually transmitted TMVII was reported in June, and “four additional TMVII infections were diagnosed between April and July 2024 in New York City among men who have sex with men.”

The rash appeared “on (patients’) face, buttocks or genitals and was successfully treated with antifungal drugs,” a dermatologist-led team said. Dr. Avrom Caplanfrom NYU Langone Health in New York City.

His team published their findings Thursday in the Morbidity and Mortality Weekly Report, a journal of the US Centers for Disease Control and Prevention.

According to the report, all five cases of sexually transmitted ringworm documented so far in the United States involved gay or bisexual men in their 30s who had multiple sexual partners.

How did TMVII get to the United States? That’s not clear, although the man whose case of the fungal infection was reported in June said he had recently traveled to several countries in Europe.

All five patients reported recent sexual contact with other men.

In all five cases, common antifungal drugs cleared the patients’ rashes.

The bottom line for clinicians, as well as sexually active people: Be aware “that TMVII can spread through sexual contact and cause lesions in the genitals, buttocks, face, trunk, or extremities,” Caplan’s team said.

They noted that only laboratory tests can confirm T. mentagrophytes infection, which some people may initially mistake for “eczema, psoriasis or other dermatological conditions.”

The infection can be treated and cured, but it takes time. According to the researchers, “Patients may require oral antifungal therapy for up to 3 months and should take treatment until the lesions resolve completely.”

This is important because as long as the rash is present, infected people must avoid skin-to-skin contact with others to avoid spreading the infection. They should also avoid sharing personal items, Caplan and team said.

Finally, they added, patients should resist the urge to use antifungal steroid creams to treat the rash because they can “make the tinea (ringworm) infection worse.”

More information

Learn more about rings at Mayo Clinic.

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