The U.S. government has confirmed the nation's first travel-related human case of New World screwworm, marking a rare but serious public health development tied to a regional livestock outbreak in Central America.

The U.S. Centers for Disease Control and Prevention (CDC) confirmed the diagnosis on August 4, following an investigation by the Maryland Department of Health, according to a statement from the U.S. Department of Health and Human Services (HHS). The patient had recently returned from El Salvador, a country affected by the ongoing screwworm outbreak.

While HHS emphasized that the public health risk remains low, discrepancies have emerged over the patient's travel origin, with beef industry sources asserting that the individual arrived from Guatemala. The CDC has not addressed the conflicting accounts, further fueling concerns across the cattle industry.

Screwworms are parasitic flies whose larvae feed on living flesh, posing severe threats to both animals and, in rare cases, humans. The infestation-if untreated-can be fatal. Though treatable, it requires the removal of hundreds of larvae and intensive wound care.

This latest case has alarmed livestock stakeholders, as screwworm infestations have moved steadily north from Central America through Mexico since 2023. The USDA estimates a potential outbreak in Texas alone could cost $1.8 billion, factoring in cattle losses, treatment, and labor.

In response, USDA Secretary Brooke Rollins recently announced a $750 million sterile fly facility to be built at Moore Air Force Base in Edinburg, Texas. The facility is expected to take up to three years to come online and aims to reproduce sterile screwworm flies to curb the pest's population.

Meanwhile, industry groups like the Beef Alliance have voiced frustration over what they perceive as a lack of transparency from federal agencies. Internal communications obtained by Reuters suggest that news of the Maryland case spread informally among state veterinarians and livestock executives before any official CDC disclosure.

"They weren't forthcoming at all," said Beth Thompson, South Dakota's state veterinarian. "We found out via other routes."

The economic implications are serious. U.S. cattle herds are at a 70-year low, and beef prices are already at record highs. A human case-however isolated-could spook markets. A Texas A&M economist has reportedly been tasked with evaluating the economic fallout tied to a border closure on Mexican cattle imports, which began in late 2024 to prevent parasite entry.

The USDA and Mexico are racing to contain the spread. In July, Mexico began building a $51 million fly sterilization facility, while the U.S. continues importing sterile flies from Panama City, home to the region's only active plant. Experts estimate that at least 500 million sterile flies must be released weekly to push screwworm populations back to the Darien Gap, the natural border between Panama and Colombia.

U.S. livestock markets remain on alert. While the screwworms were eradicated domestically in the 1960s using sterilization techniques, the parasite remains endemic in Cuba, Haiti, the Dominican Republic, and South America.

With the first human case now confirmed and the pest edging closer to the U.S. border, the risk-while currently low-could escalate without swift, coordinated containment.