Experts Warn of New, Difficult-to-Treat Fungal Skin Infections Emerging in US

New strains can look different from typical ringworm, making them harder to diagnose.
A close view of a ringworm infection. CDC/ Dr. Lucille K. Georg
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Two highly contagious ringworm strains that defy standard treatments are arriving in the United States, according to a new report by NYU Langone Health, a medical center chain in New York City.

The fungi are rare, making them difficult to diagnose. They also defy standard treatments and are harder to treat. These factors give ringworm infections the potential to spark an epidemic. Therefore, health care providers are urged to be on high alert.

New Strains Are Harder to Diagnose

The NYU Langone Health report references two case studies.
The first, published in JAMA Dermatology, describes a man in his 30s who developed Trichophyton mentagrophytes type VII (TMVII), a common fungus that causes ringworm, after returning home to New York from a trip to Europe and California.
This strain takes longer to treat than a typical ringworm infection and has been increasingly diagnosed in Europe. Evidence suggests it is sexually transmitted, particularly among men who have sex with men. Southeast Asia might have been the starting point of TMVII spread, with documentation supporting that the first reported cases in Europe were associated with travel to that region.
The second case study, also published in JAMA Dermatology, describes 11 patients in New York City treated for ringworm caused by Trichophyton indotineae (T. indotineae). This drug-resistant fungal strain is not sexually transmitted. The study found that this fungus often resists standard antifungal therapies, including terbinafine, and some patients may require alternative treatments.
Treating antifungal-resistant ringworm, which has already spread worldwide, might require prolonged antifungal therapy lasting over three months with itraconazole or other systemic drugs, according to the U.S. Centers for Disease Control and Prevention (CDC).

Doctors Should Be Vigilant: Researchers

Although rates of TMVII and T. indotineae infections are currently low in the United States, the researchers urge health care providers to be vigilant for signs and symptoms, especially in sexually active patients, recent travelers, or those with unexplained itchy rashes.

“Healthcare providers should be aware that Trichophyton mentagrophytes type VII is the latest severe skin infection to reach the United States,” Dr. Avrom Caplan, an assistant professor in the Department of Dermatology at NYU Grossman School of Medicine, said in a press release, urging providers to ask about groin and buttocks rashes in at-risk patients directly. His team is expanding research efforts to track emerging cases.

While not typically life-threatening, these infections can be challenging to treat, causing discomfort and potential complications if left untreated, including permanent hair loss, scarring, and deeper skin penetration.

US Cases First Reported in 2023

According to the new report, the first T. indotineae infections in the United States were reported in March 2023, when Dr. Caplan sent samples from two ringworm infections to a New York state public health laboratory. The lab used genomic sequencing, a method used to determine the entire genetic makeup of a cell, to identify the isolates as T. indotineae.

The cases were initially detected in New York in 2021 and 2022 and involved two women. One had recently traveled to Bangladesh, while the other woman had no travel history to explain how she became infected, suggesting the disease was already present in the United States.

According to the CDC, there are likely more infected patients who have not received a diagnosis or have received an incorrect diagnosis.

Crop Fungicides Fueling Severe Fungal Infection Outbreak: Doctor

An epidemic of severe, antifungal-resistant tinea (fungal skin infections) originated in South Asia due to the rapid spread of the treatment-resistant strain T. indotineae, then spread over the past 10 years, according to the CDC. The problem is likely driven by the misuse and overuse of topical antifungals and corticosteroids.
However, agricultural fungicides could be another potential culprit, Dr. Norman Ng from the Department of Emergency Medicine at Staten Island University Hospital in New York told The Epoch Times. Fungi impact global agriculture, with a quarter of crops lost to fungal diseases.

“Farmers use fungicides to combat these, but this can lead to resistance in human-infecting fungi due to shared molecular targets between fungicides and antifungal drugs,” Dr. Ng said.

Developing new antifungals is challenging due to the genetic similarities between fungi and humans, making it difficult to target fungi without harming human cells, he noted.

Fungi develop drug resistance quickly, and only three major classes of antifungal drugs exist compared to dozens of antibacterial classes. “We urge providers to continue to practice antimicrobial stewardship in order to slow down the spread of multi-drug-resistant infections,” Dr. Ng said.

George Citroner
Author
George Citroner reports on health and medicine, covering topics that include cancer, infectious diseases, and neurodegenerative conditions. He was awarded the Media Orthopaedic Reporting Excellence (MORE) award in 2020 for a story on osteoporosis risk in men.