A drug-resistant fungus responsible for a persistent and widespread form of ringworm is increasingly being detected in new geographical areas, prompting a global public health alert. The strain, identified as Trichophyton indotineae, can cause painful, extensive rashes that resist standard antifungal treatments.
Scientists analyzed over a million samples from 54 countries collected between 2022 and 2025. Their findings, published in Emerging Infectious Diseases, indicate a significant rise in cases, with seven times more detections in 2025 compared to 2022. The study identified the fungus in at least five European and South American countries where it had not been previously reported. While the majority of detected cases were in Europe, the study also noted a small number of detections in North America.
In the United States, this specific fungus strain was first identified in 2023 in two patients in New York City whose infections did not respond to common treatments. According to the Centers for Disease Control and Prevention (CDC), the strain has since been detected in 11 states, though the agency acknowledges this figure is likely an undercount, as some cases may be misdiagnosed or not tested.
Ringworm, commonly known as athlete's foot or jock itch depending on its location, is a highly contagious fungal infection. While most cases are treatable with topical lotions or antifungals, T. indotineae presents a challenge due to its resistance to conventional therapies. Warning signs for this strain include red, itchy rashes covering large skin areas that do not improve with over-the-counter creams or oral antifungals, or that repeatedly return over several months.
The fungus was initially identified in India in 2020 following a prolonged outbreak. Since then, it has caused significant outbreaks in South Asia and has been documented in numerous Western countries. Researchers suggest that international travel, particularly air travel, may be a key factor in its global dissemination.
The CDC is actively monitoring three emerging fungal strains that can cause severe ringworm infections: T. indotineae, a terbinafine-resistant Trichophyton rubrum, and TMVII. T. indotineae and the terbinafine-resistant T. rubrum are of particular concern due to their potential to evade common antifungal drugs. TMVII is more often associated with sexual contact.
Health authorities are urging individuals with ringworm infections that do not improve, especially after using standard treatments, to consult a healthcare provider. Prompt medical attention is also advised for rashes that spread, are painful, become pus-filled, recur frequently, or appear on the genitals, groin, buttocks, or face.