Highly contagious form of sexually transmitted ringworm reported in the US for the 1st time

The infection, which can take months to clear up even with treatment, has been increasingly diagnosed throughout Europe.
Posted at 10:01 PM, Jun 05, 2024

Health care officials are sounding the alarm after a man became the first person in the U.S. to contract a rare form of highly contagious, sexually transmitted ringworm.

The New York City resident in his 30s had recently returned home from a trip to England, Greece and California when he developed tinea — a fungal skin infection also known as ringworm — on his penis, buttocks and limbs, NYU Langone Health researchers said in a press release.

The researchers' report, published Wednesday in JAMA Dermatology, states genetic testing of the man's rashes revealed they were caused by Trichophyton mentagrophytes type VII, a sexually transmitted species of ringworm that's been increasingly diagnosed throughout Europe but never identified in the U.S.

There were 13 reports of TMVII in France last year, mostly in men who had sex with men, researchers stated. The U.S. resident said he had sex with multiple male partners while traveling, but none reported similar skin issues.

The skin rash caused by the new fungus is easily spreadable on the face, limbs, groin and feet. But it can look different from the familiar circles seen in most forms of ringworm and may instead be confused for eczema-caused lesions, leading to delay of proper treatment, the researchers said.

The American patient's infection took 4 1/2 months to heal, even with treatment — a normal duration for TMVII-caused infections. Ultimately, three different antifungals were used for weeks at a time to eradicate the fungus.

A CDC illustration of ringworm symptoms

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So although the skin condition is difficult to treat, it's possible. Yet the case is still alarming to some physicians because of the increasing difficulty in treating similar fungal infections, leading some to think ringworm is an emerging public health threat.

Last year, the U.S. saw its first two cases of ringworm caused by Trichophyton indotineae, a highly contagious infection causing similar itchy rashes as TMVII, but that is resistant to antifungal treatment. These infections have spread rapidly in South Asia, with the CDC reporting this is due to misuse and overuse of topical antifungals.

NYU Langone researchers conducted another study, published in JAMA Dermatology in May, that looked into ringworm caused by T. indotineae in 11 men and women. The patients were treated for the infection in New York City hospitals from May 2022 to May 2023.

The study found that mutations in the fungus' genetic code often prevented the antifungal terbinafine from fighting the infection. When the patients who were resistant to terbinafine were treated with another antifungal called itraconazole, many recovered or improved. However, itraconazole was found to interfere with many other medications and caused side effects that would make it hard to use for extended periods.

"These findings offer new insight into how some of the fungal skin infections spreading from South Asia can evade our go-to therapies," said study lead author and dermatologist Dr. Avrom Caplan. "Beyond learning to recognize their misleading signs, physicians will need to ensure their treatment addresses each patient's quality-of-life needs."

Caplan said he plans to work with leading fungi experts in the U.S. and globally in the next few months to track emerging cases and deepen research.

And although rates remain low in the U.S. as of now, researchers caution dermatologists to be on alert for signs of TMVII and T. indotineae in patients and to directly ask them about rashes around the groin and buttocks, "especially for those who are sexually active, have recently traveled abroad and report itchy areas elsewhere on the body," study senior author Dr. John Zampella said.