A new form of rare, sexually transmitted ringworm has been reported in the United States.

Health officials are warning of a new case of ringworm, likely transmitted through sex, reported in New York City. It is the first such case in the United States.

The infection, a rare fungus called Trichophyton mentagrophytes type VII (TMVII), was found in a man in his 30s who said he had sex with multiple men during a trip to England, Greece and California, according to a study published Wednesday in JAMA Dermatology by doctors at NYU Langone Health in New York City.

When the man returned from his trip, he developed a red, itchy rash on his penis, legs, groin and buttocks. The rash resembles eczema, a common condition that causes dry, itchy and inflamed skin, as opposed to the typical ring-shaped fungal infection of the skin.

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A person with eczema resembling Trichophyton mentagrophytes type VII (TMVII). (BSIP/UIG via Getty Images)

Tests revealed he had the fungus and doctors prescribed conventional oral antifungals – but it took his body four and a half months to get rid of the fungus.

The man took fluconazole for four weeks without improvement before switching to terbinafine for six weeks and then itraconazole for eight weeks.

Doctors say he hasn’t had any other infections that could have made the problem worse.

Dr. Avrom Caplan, assistant professor of dermatology at NYU Grossman School of Medicine and author of the new report, told NBC that there is no cause for public concern.

“There’s no evidence that this is widespread or that this is something that people really need to be concerned about,” Caplan told the outlet. “But if people have itchy rashes in areas like the groin and it’s not getting better, they should see a doctor.”

John Zampella, also a co-author of the study, asked doctors for help in identifying the fungus.

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The study’s co-author asked doctors for help in identifying the fungus. (iStock)

“Because patients are often hesitant to discuss genital problems, physicians need to ask directly about rashes in the groin and buttocks, especially in sexually active patients who have recently traveled abroad and report itchy areas elsewhere on the body,” Zampella said in the statement.

The man’s case is the first recorded in the U.S. and comes after doctors in France reported 13 such cases last year, a statement about the study said. Twelve of those patients were men who had sex with men. The man said he had sex with several male partners during his travels, none of whom reported similar skin problems.

Caplan said the infection was most likely transmitted through sexual contact, but he could not rule out the possibility that he caught the fungus in a sauna he visited two months before symptoms began, NBC reported.

According to the study, there has been an increase in fungal infections of male reproductive organs in India, which is consistent with the emergence of a slightly different form of ringworm called Trichophyton indotineae.

Climate, hygiene and bathing habits probably contribute to the spread of this fungus, as does sexual contact.

Caplan had previously identified the first two cases of Trichophyton indotineae, and since then his team at NYU Langone Health has identified nine more cases of ringworm in men and women in New York City.

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The study was conducted by physicians at NYU Langone Health in New York City. (Noam Galai/Getty Images)

The infection causes rashes similar to TMVII that are itchy and contagious, and it poses a greater challenge for dermatologists because it often resists treatment with terbinafine, Caplan said.

“These findings provide new insight into how some of the fungal skin infections originating in South Asia can evade our standard therapies,” Caplan said. “Physicians must not only learn to recognize their misleading signs, but also ensure that their treatment meets the quality of life needs of each patient.”

Caplan said he plans to work with leading fungal experts in the U.S. and internationally over the next few months to expand research efforts and track emerging cases.