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At least 2 cases of drug-resistant ringworm infections found in the U.S., CDC says

Cases of the infection had surged in South Asia over the past decade.
Trichophyton Rubrum
A micrograph of the fungus Trichophyton rubrum, which causes ringworm. A drug-resistant species of the Trichophyton fungus was recently detected in the U.S.CDC via Getty Images

Two cases of highly contagious, drug-resistant ringworm infections have been detected in New York City — the first such cases reported in the U.S., the Centers for Disease Control and Prevention reported Thursday.

The infection was first identified in a 47-year-old woman who had developed a bad case of ringworm, also known as tinea, while traveling in Bangladesh.

A rash had erupted across most of her body and typical antifungal creams did nothing to alleviate it.

"My radar went up immediately," said Dr. Avrom Caplan, an assistant professor of dermatology at NYU Grossman School of Medicine, who treated the patient and was one of the report's authors.

The woman's infection turned out to be caused by a relatively new species of ringworm-causing fungus, called Trichophyton indotineae. Over the past decade, infections from this drug-resistant fungus have spread rapidly in South Asia, likely driven by overuse of medications to treat them, including topical antifungals and corticosteroids, the CDC report said.

The woman's case spurred Caplan to ask his colleagues if they had seen similar infections. He soon discovered a second case in a 28-year-old New York woman.

That woman had developed ringworm across much of her body during the summer of 2021. In this case, however, the patient had not traveled outside the U.S.

Neither woman had underlying health conditions that might increase their risk for drug-resistant infections.

Caplan alerted public health officials about the two cases in February. Outside Asia, cases have been identified in Europe and Canada.

Trichophyton indotineae's emergence in the U.S. did not surprise Dr. Jill Weatherhead, an assistant professor of infectious diseases and tropical medicine at Baylor College of Medicine in Houston.

"We've learned over the years, especially with the Covid pandemic, that something happening in another part of the world is likely to happen in our part of the world at some point," said Weatherhead, who was not involved with the new report.

Like drug-resistant bacteria, drug-resistant fungi are a serious public health concern. Cases of Candida auris, another type of drug-resistant fungal infection, have been spreading in health care facilities in the U.S. That infection is extremely difficult to treat and can be deadly.

"We're always so focused on antimicrobial resistance as it relates to bacteria that we forget that those rules also apply to fungi," said Dr. Adam Friedman, professor and chair of dermatology at the George Washington University School of Medicine & Health Sciences.

Friedman, who was not involved with the new report, said he has witnessed an uptick in patients with fungal infections whose conditions either take longer to respond to usual treatments or require additional medications.

"If you are treating something with a drug that you expect would work, but it doesn't get better, you need to go back to the drawing board," he said.

What is ringworm, and how is it treated?

Ringworm is not caused by a worm, as the name would suggest. It is a fungal infection. It spreads easily through skin-to-skin contact and usually looks like a circular pattern of raised, itchy scales. It can pop up on the face, chest, scalp or groin area. Ringworm can occur at any age but is more common in children.

Typically, cases are treated with antifungal creams. But some particularly difficult cases require antifungal medications, such as terbinafine or itraconazole, taken in pill form.

The two New York patients detailed in the CDC report were successfully treated with the oral drugs. But the medications, especially itraconazole, require a physician's care. The drug can cause heart failure and should not be taken with certain medications, according to the National Library of Medicine.

Caplan said that he suspects there may be other U.S. cases of Trichophyton indotineae. The husband and son of the 47-year-old patient, for example, have also developed ringworm, and are undergoing testing to see if the fungi are the same.

At this point however, he said, Trichophyton indotineae "is not a widespread problem" in the U.S.

Caplan suggested people with suspected ringworm infections contact a dermatologist for evaluation. He also recommended washing linens, clothes and towels regularly to minimize the spread of the fungi.

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