The United States has logged its first travel-associated human infection with New World screwworm in decades, federal health officials said. The case involves a Maryland resident who recently returned from El Salvador, according to the Department of Health and Human Services. The patient was treated after laboratory testing at the Centers for Disease Control and Prevention confirmed the parasite on Aug. 4. Maryland health authorities report the individual has recovered and no secondary cases have been detected. HHS spokesperson Andrew G. Nixon said the "risk to public health in the United States from this introduction is very low," noting that the parasite does not spread from person to person. The flesh-eating screwworm fly was eradicated from the United States in the 1960s, but outbreaks among cattle have been advancing north from Central America into southern Mexico since 2023. Female flies lay eggs in wounds of warm-blooded animals; larvae burrow through living tissue and can be fatal if untreated. While no U.S. livestock infections have been reported this year, the agriculture sector is on alert. The Department of Agriculture estimates a full-blown outbreak could cost Texas alone about $1.8 billion in animal deaths, treatment and labor. To head off that threat, USDA plans to build a sterile-fly production facility in Edinburg, Texas, reviving a technique that previously helped wipe out the pest across North America. Beef traders say any sign of domestic transmission could jolt already tight cattle markets.