A person in Maryland is confirmed to have a screwworm living in them. It is the first case in the U.S. in several years.

The person, who was not identified, had traveled to the U.S. from El Salvador, Anderw Nixon, a Department of Health and Human Services spokesperson, said, according to The Washington Post.

Initially, it was said a person who tested positive had traveled from the U.S. to Guatemala, and a person with the Beef Alliance sent an email to about 24 people alerting them to the confirmed case, Reuters reported.

There is an outbreak of New World screwworm in Central America that has raised concerns that it could spread to the U.S. and affect the cattle industry. Health officials said they are not concerned about a human outbreak.

A screwworm is a flesh-eating parasitic blowfly. It lives on the living tissue of warm-blooded animals.

It can live in a human, but it is rare.

A female New World Screwworm blowfly will lay her eggs in wounds, Reuters reported. The Associated Press said they can also be laid in other body openings, such as the ears. When the eggs hatch, the larvae chew through the flesh, feeding on it in a pattern that resembles a screw being driven into wood. If left untreated, the larvae, or maggots, will kill the host, Reuters reported.

There is no existing treatment, other than prevention and the quick removal of potentially hundreds of larvae.

Screwworms have been mostly extinct in the U.S. for the past 50 years, the Food and Drug Administration said.

About a week before this case, the Department of Agriculture had announced plans to release sterile flies to prevent screwworms from reproducing. The program is expected to cost $8.5 million and will be done in Texas, the Post reported.

As for the person who was infected, they were treated and preventive measures were taken in the state, Reuters reported, but did not provide details. The person’s condition was not released, the AP reported.

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