The emergence of Trichophyton mentagrophytes genotype VII (TMVII), an inflammatory dermatophyte increasingly associated with intimate skin-to-skin contact, is drawing heightened attention from infectious disease specialists and public health officials, who say clinical laboratories will play a critical role in identifying infections and supporting surveillance.
Although TMVII has frequently been described as a sexually transmitted infection, or STI, transmission is not limited to sexual activity, Jason Zucker, MD, assistant professor of medicine at Columbia University and assistant medical director of the New York City STD Prevention Training Center said, speaking on the Going anti-Viral podcast produced by International Antiviral Society–USA. "[TMVII] is transmissible to people who have close skin-to-skin contact," he said, highlighting the potential for spread beyond sexual encounters.
Recent cases have predominantly involved gay and bisexual men and other men who have sex with men, many of whom sought care through sexual health clinics, Zucker said. However, he emphasized that anyone can become infected through close skin-to-skin contact. Though less common, this can include transmission through contaminated items such as towels, bedding, clothing, razors, or shared personal objects.
Distinguishing TMVII from common ringworm
TMVII causes ringworm but often presents differently from more typical dermatophyte infections. Patients may develop painful, inflammatory, coin-shaped lesions affecting the genitals, perianal region, buttocks, trunk, thighs, face, arms, or legs, making the infection easy to mistake for bacterial skin infections or other sexually transmitted diseases.
On the Going anti-Viral podcast, Zucker noted that TMVII differs from classic ringworm in both its epidemiology and clinical pattern, i.e., being linked to close physical or sexual contact and tending to produce more inflammatory lesions in anatomic sites not commonly associated with traditional dermatophyte infections.
The infection first came to international attention in 2023 after cases were reported in Europe among men who had recently traveled to Southeast Asia. The first US case was reported in New York in 2024, according to public health surveillance reports, with subsequent cases detected in several cities.
Minnesota has reported the country's largest documented cluster to date. Since the first confirmed case in July 2025, the Minnesota Department of Health has identified 13 confirmed cases and 27 suspected cases in the Twin Cities metropolitan area through enhanced surveillance.
"The first cases of TMVII in Minnesota were identified by astute clinicians who proactively notified the health department and requested confirmatory testing," the Minnesota Department of Health said in a public health update.
Laboratory diagnosis of TMVII is essential
For laboratory professionals, diagnosing TMVII presents unique challenges. According to CDC guidance, potassium hydroxide (KOH) preparation of skin scrapings can confirm a dermatophyte infection but cannot distinguish TMVII from other fungal species. Definitive identification requires advanced molecular methods, including sequencing, performed by select academic, commercial, and public health laboratories.
There is growing resistance to terbinafine among dermatophytes causing classic ringworm, Zucker said, so if a patient is not improving on terbinafine, obtaining a culture early can help clarify the underlying pathogen and guide management.
Because prior antifungal therapy can reduce diagnostic yield, specimens should be collected before treatment whenever feasible. While clinicians may begin empiric therapy based on clinical suspicion, laboratory confirmation remains important for surveillance and epidemiologic monitoring.
Researchers at Duke Global Health Institute warn that limited awareness may allow infections to go undetected.
"TMVII can resemble other skin conditions or sexually transmitted infections, so proper evaluation is important," Tom Carpino, PhD, Hock postdoctoral research fellow at the Duke Global Health Institute said in a recent article. "The lack of awareness among the highest risk individuals and communities, combined with the lack of wide-scale testing and reporting from clinics, are ingredients for a very serious epidemic to go under the radar."
Most TMVII infections respond to oral terbinafine, although treatment may extend for several weeks or as long as three months, and clinicians should closely monitor response. As awareness grows, experts say expanded laboratory testing, timely reporting, and strengthened surveillance will be essential to defining the true burden of this emerging fungal infection and supporting prompt diagnosis and treatment.
This article was created with the assistance of Generative AI and has undergone editorial review before publishing.
