Drug-Resistant Fungus Trichophyton indotineae Spreads to 29 Countries, Cases Surge Sevenfold
核心洞察
A global analysis of 1.6 million fungal samples from 54 countries found Trichophyton indotineae (搜索) infections rose from 237 in 2022 to 1,692 in 2025, a sevenfold increase.
The drug-resistant ringworm strain, resistant to the common antifungal terbinafine, was detected in at least five new countries, including Bulgaria, Croatia, Colombia, Luxembourg and Uruguay.
Researchers warn the fungus is a "rapidly evolving international issue" and urge health authorities to address the growing public health challenge associated with therapeutic difficulties.
A drug-resistant fungus that causes an itchy, widespread rash is spreading to new regions of the world, with global detections surging roughly sevenfold in just three years, according to a new study published in the CDC's Emerging Infectious Diseases.
Trichophyton indotineae (搜索), a strain of the fungi responsible for ringworm, resists standard antifungal treatments and has now been identified in 29 countries, including the United States, Canada and the United Kingdom. Researchers analyzing more than 1.6 million samples from 54 countries found that infections rose from 237 in 2022 to 1,692 in 2025 — a trend the study authors described as "a marked global increase."
The fungus was first identified in north India in 2020 following a yearslong outbreak of a difficult-to-treat ringworm strain in the area, though some reports trace its initial identification to 2008. Since then, it has caused major outbreaks in South Asia and spread to many Western countries.
A Growing Global Footprint
In their analysis of samples collected between 2022 and 2025 and held in a global database in France, researchers found 3,399 samples from 29 countries — or 0.2 percent of the total — tested positive for the drug-resistant strain. Of these, 63 percent came from Europe, 16.8 percent from Asia, 15.7 percent from South America, 1.6 percent from North America, and 0.5 percent from Africa.
The strain was detected in at least five countries where infections had not previously been reported: Bulgaria, Croatia, Colombia, Luxembourg and Uruguay. In western and northern Europe, where the most cases were detected, the fungus was found in both urban and rural areas.
In the United States, the strain was first detected in 2023 in two unrelated patients in New York City whose infections did not respond to standard treatments. It has since been detected in 11 states, according to the Centers for Disease Control and Prevention (搜索) (CDC), though the agency notes this is likely an undercount, as cases may be misdiagnosed or not tested in some states.
Resistance and Clinical Presentation
Unlike most ringworm cases, which are easily cleared with a short course of lotions or antifungals, T. indotineae can cause a painful rash that spreads over much of the body and resists standard treatments. The fungus is resistant to terbinafine, a commonly used antifungal.
Ringworm is caused by 40 species of fungi and is an extremely common infection, also known as athlete's foot when it occurs on the feet or jock itch when it appears on the groin. Estimates suggest about 14 percent of Americans are infected at any given time, as the fungi can easily spread via skin-to-skin contact and through contact with towels, bedsheets and surfaces in bathrooms or public locker rooms.
Warning signs of a T. indotineae infection include a rash that is red, itchy and covers a large area of skin, does not improve after standard treatment — over-the-counter creams or oral antifungals — or keeps recurring over several months. The only way to confirm an infection is through a lab test.
Public Health Implications
Researchers cautioned that their tally is an undercount, noting that many infections are never formally diagnosed or submitted to the dataset, and that multiple samples may have been submitted for the same patient. The database used in the study received no data from virtually any country in Africa, the Middle East and South Asia.
The team warned that the difficult-to-treat strain is likely spreading via international travel, with infected individuals boarding airplanes. "Our results reveal a marked global increase in T. indotineae cases," the researchers wrote. "Health authorities should address this rapidly evolving international issue."
The CDC is currently tracking three emerging fungi that could cause serious ringworm infections — T. indotineae, terbinafine-resistant Trichophyton rubrum (搜索) and TMVII. The agency notes that T. indotineae and terbinafine-resistant T. rubrum are particularly concerning because they may not be cleared using typical antifungal drugs, while TMVII is more commonly linked to sexual contact.
Doctors urge anyone with a ringworm infection that is not improving — especially after using over-the-counter treatments — to speak to a healthcare provider. Individuals with a rash that is spreading, painful or pus-filled, that keeps returning, or that appears on the genitals, groin, buttocks or face are also urged to seek treatment.