A ringworm skin rash caused by an infection of the fungus TMvii, which has emerged in some parts of the U.S. in the past year.
Published March 27, 2026 under Research News
Infectious disease experts at the Duke Global Health Institute (DGHI) are working to educate doctors about a new sexually transmitted infection (STI), which recently caused an outbreak of at least 30 cases in Minnesota and has been detected in other U.S. cities.
The infection, caused by the fungus Trichophyton mentagrophytes type VII (TMvii), spreads through intimate contact and has predominately been seen among sexually active gay men. It causes painful, coin-sized rashes on the arms, buttocks, trunk, legs and genitals. While infections can be treated with oral antifungal medications, treatment can take several weeks, making fast detection of the uncommon infection critical.
“TMvii can resemble other skin conditions or sexually transmitted infections, so proper evaluation is important,” says Tom Carpino, Ph.D., the Hock postdoctoral research fellow at DGHI, who has studied the public health challenges of emerging STIs such as mpox. “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.”
TMvii infections were identified in 2023 in Europe among men who had recently traveled in Southeast Asia. The first U.S. case was reported in New York in 2024, with a handful of cases arising in other U.S. cities. The Minnesota outbreak, which began in July 2025, is the largest recorded in the U.S., leading the state health department to issue a public health alert in February.
Carpino recently consulted with the U.S. Centers for Disease Control and Prevention (CDC) to put together information about TMvii infections for clinicians and the public. DGHI spoke with Carpino in late March to learn more about the infection and how health officials are responding. The conversation has been edited for length and clarity.
Is this a brand new infection? How did it arise?
TMvii isn’t a completely new organism, but it is an emerging strain that’s only recently been recognized in human outbreaks. It was first identified in 2023, primarily among men who had traveled in Southeast Asia, which suggests it may have been circulating undetected before being more formally characterized. What we’re seeing now reflects improved detection as well as potential spread through connected sexual and social networks.
How does TMvii spread?
TMvii spreads primarily through direct skin-to-skin contact, including during sex. It can also spread through shared items like towels, clothing, or bedding, though this appears to be less common. Because the infection often affects areas of close contact, transmission during intimate encounters is a key driver.
What are the symptoms of an infection, and how quickly do they emerge?
Symptoms can vary. Some people develop mild redness or ringworm-like rashes, while others experience more severe, painful, or pustular lesions. These can appear on the genitals, buttocks, trunk, or extremities. Based on early data, symptoms may develop anywhere from several days to a few weeks after exposure, though this is still being studied.
What should someone do if they suspect an infection?
If someone notices a persistent or unusual rash, especially in the genital region, they should seek medical care. TMvii can resemble other skin conditions or sexually transmitted infections, so proper evaluation is important. Diagnosis may require laboratory testing, and treatment often involves oral antifungal medications such as terbinafine.
State health officials are advising people who see signs consistent with TMvii rashes to seek prompt treatment. Although the infection is treatable with oral antifungal medications, patients may require up to three months of treatment. Some patients may develop painful and persistent rashes that can lead to scarring and worsening infections without prompt treatment.
From a public health perspective, what can be done to prevent a wider outbreak?
Early recognition and awareness are critical. Clinicians need to be aware of TMvii so they can diagnose and treat cases promptly. Public health messaging should focus on reducing stigma while providing clear guidance on symptoms and when to seek care. Strengthening surveillance, particularly in dermatology and sexual health clinics, will also help us better understand how widely this infection is circulating and how best to respond.
Stigma is always a concern with any outbreak affecting marginalized communities. What should health officials be doing to ensure stigma doesn’t become a barrier to seeking treatment?
Public health officials should emphasize that anyone can get TMvii. Even if you don’t think it’s TMvii, if you have a new rash or lesion, particularly in the genital region, you should seek medical care. Any ringworm-like rash should be taken seriously, and you should consult with a medical provider for immediate treatment to prevent complications.
