Two cases of drug-resistant ringworm infections were reported in New York City, the first such cases in the U.S., the Centers for Disease Control (CDC) announced on Thursday.

The infection, which is highly contagious, was present in two patients in the city who did not improve with typical treatments. One, a 28-year-old woman, developed a rash in the summer of 2021 across much of her body. Another, a 47-year-old woman, developed a rash across most of her upper body.

The second woman had traveled outside of the U.S., making a trip to Bangladesh, where she developed the rash. The other had no recent international travel history. Neither of the women had underlying health conditions.

A New York dermatologist alerted public health officials of the cases in February, identifying their infections as T. indotineae, a novel form of ringworm that has emerged in South Asia. The infection usually takes on widespread and inflamed plaques on the body, particularly the public region, thighs and the face. It is frequently resistant to typical treatments.

The discovery of the infections is worrying for public health officials as they are the first reported in the U.S., after cases had been reported in Asia, Europe and Canada.

The CDC said the fact that the woman who had no recent international travel history was found to have the infection was alarming, indicating it could be a “potential local U.S. transmission.”

The agency said health care providers should be prepared to provide up to 12 weeks of therapy if the fungus that causes the condition is found.