A drug-resistant fungus that can cause a rash covering most of the body is spreading to new areas of the world, including within the US, a study suggests.
Ringworm is a highly contagious disease that causes an itchy, circular rash on the skin, typically on the foot or groin. Rather than being caused by a worm, it is actually caused by 40 species of fungus.
While most cases are easily cleared with a short course of lotions or antifungals, in recent years doctors have grown increasingly alarmed over a new strain – Trichophyton indotineae – that can cause a painful rash which spreads over much of the body and resists standard treatments.
Now, scientists in Europe have analyzed samples from patients globally to track the spread of the strain and detect whether it is being found in new areas.
In their analysis of more than a million samples from 54 countries, researchers found scientists were now detecting seven times as many cases as in 2022 globally.
The strain was also detected in at least five new countries in Europe and South America over the last five years where it had not been previously reported.
In the US, the fungus strain was first detected in 2023 in two unrelated patients in New York City whose infections did not respond to standard treatments.
It has now been detected in 11 states, according to the Centers for Disease Control and Prevention (CDC), but the agency says this is likely an undercount, adding that cases may be misdiagnosed or not tested in some states.
The above shows locations where Trichophyton indotineae has been detected nationwide. Countries that are colored green have not submitted any data
Ringworm is an extremely common infection, also known as Athlete’s foot when it is on the feet or jock itch if it is on the groin.
About 14 percent of Americans are infected at any given time, estimates suggest, which is because the fungi can easily spread via skin-to-skin contact and touching towels, bedsheets and surfaces in bathrooms or public locker rooms also touched by an infected person.
Anyone can be infected with ringworm, but those who take part in contact sports such as wrestling, sweat excessively or use public locker rooms are at higher risk of suffering a ringworm infection. Anyone with a weakened immune system or autoimmune disease is also at higher risk from an infection.
The only way to confirm a T. indotineae infection is to do a lab test. But doctors say there are warning signs that someone may be infected with this strain.
These include having a rash that is red, itchy and covers a large area of skin and does not improve after standard treatment – over-the-counter creams or oral antifungal – or that keeps recurring over several months.
The new fungus was formally detected in north India in 2020 following a yearslong outbreak of a difficult-to-treat ringworm strain in the area.
Since, it has caused major outbreaks in South Asia and been detected in many western countries.
To track its spread, for the new study scientists analyzed 1.6 million samples from patients suspected to have a fungal infection that were held in a global database in France.
The above shows where T. indotineae is present in Europe (Red countries)
The above shows how the number of samples testing positive for the fungus has increased by year
The samples had come from 54 countries and were all collected between 2022 and 2025.
Overall, the researchers found 3,399 samples from 29 countries, or 0.2 percent of the total, tested positive for the new drug-resistant fungus strain.
Of these, 63 percent came from Europe, 16.8 percent came from Asia, 15.7 percent from South America and 1.6 percent from North America. A further 0.5 percent were from Africa.
In western and northern Europe, where the most cases were detected, the strain was detected in both urban and rural areas.
Over the study period, the number of infections with the difficult-to-treat strain also increased ‘ominously’ by year, according to the researchers.
In 2022, there were 237 detections in the database, they said. But by 2025, this had surged to 1,692.
In the study, the fungus was also detected in at least five countries where infections had not previously been reported. These included Bulgaria, Croatia, Colombia, Luxembourg and Uruguay.
A small number of cases were also detected in the US, fewer than were detected in Canada.
The above image shows a man infected with the emerging strain of ringworm in India
Shown above is a stock image of a ringworm infection on the chest and arms
The study did not say in which states it had been detected but previous reports show the strain has been detected in New York, Pennsylvania, California and Virginia among others.
Researchers warned their tally was an undercount, saying many infections are never formally diagnosed or submitted to the dataset. In some cases, it is also possible that multiple samples were submitted for the same patient.
The database they used had received no data from virtually any countries in Africa, the Middle East and South Asia.
Researchers warn that the difficult-to-treat strain is likely spreading via international travel where infected people board airplanes.
Publishing their study in the CDC’s Emerging Infectious Diseases, the team warned: ‘Our results reveal a marked global increase in T. indotineae cases.
‘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 and TMVII.
The agency says T. indotineae and terbinafine-resistant T. rubrum are particularly concerning because they may not be cleared using typical antifungal drugs. TMVII is more commonly linked to sexual contact.
They warn these can cause rashes on the genitals, buttocks, groin, face, trunk, arms or legs.
Doctors urge anyone who has a ringworm infection that is not improving, especially after the use of over-the-counter treatments, to speak to a healthcare provider.
Anyone who has a ringworm rash that is spreading, painful or pus-filled, a rash that keeps returning or one that is on the genitals, groin, buttocks or face is also urged to seek treatment.
