A drug-resistant strain of ringworm fungus known as Trichophyton indotineae has spread to 29 countries, according to a study published last month in the Centers for Disease Control and Prevention journal Emerging Infectious Diseases.
Unlike standard ringworm infections that typically clear with a short course of over-the-counter creams, Trichophyton indotineae causes severe, widespread rashes that resist terbinafine, a standard frontline antifungal medication. Scientists from Europe analyzed database submissions from more than 500 users across 54 countries to map the expanding geographic footprint of the pathogen.
Global Spread and Geographic Distribution
The analysis utilized records from the Mass Spectrometry Identification (MSI) project, a global database hosted by the Pitié-Salpêtrière University Hospital’s Parasitology-Mycology Laboratory in France. According to the study, total positive identifications in the database rose from 237 cases in 2022 to 1,692 cases in 2025. Across the entire three-year sampling period, 3,399 samples tested positive for the resistant strain, accounting for roughly 0.2 percent of all fungal submissions.
Geographically, the detections were heavily concentrated in Europe. Data breakdown reveals that 63 percent of the positive samples originated from European countries, followed by 16.8 percent from Asia, 15.7 percent from South America, 1.6 percent from North America, and 0.5 percent from Africa. The fungus newly appeared in at least five nations during the tracking window: Bulgaria, Croatia, Colombia, Luxembourg, and Uruguay.
In the United States, the Centers for Disease Control and Prevention notes that the strain was first identified in 2023 in New York City among two unrelated patients whose infections failed standard therapies. Health officials have since confirmed cases across 11 states. Study authors cautioned that these figures represent an undercount, as mass spectrometry equipment is unavailable in many global regions, and many routine clinical cases go untested or unreported.
Clinical Impact and Transmission
Ringworm is a misnomer, as the condition involves no worms at all; it is a general term for dermatophyte fungal infections that produce circular skin rashes, athlete’s foot, or jock itch. Approximately 40 different species of fungi cause these conditions, which typically transmit through direct skin contact or contaminated surfaces such as damp gym floors, towels, and bedsheets.
However, Trichophyton indotineae behaves more aggressively than traditional strains. Patients infected with the pathogen often develop red, intensely itchy rashes that cover expansive areas of the body and persist for months despite standard oral and topical therapies. Researchers warn that infected travelers carrying the pathogen internationally are accelerating its transmission across urban and rural borders alike, creating an emerging public health challenge that requires heightened clinical surveillance and laboratory testing.
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