London, UK, August 30, 2025

An alarming new report has surfaced from US health authorities, who have detected the first human case of the flesh-eating New World screwworm in decades, with the patient having recently returned from Central America. The discovery has put the US Department of Agriculture (USDA) on high alert, as the parasite, though rare in humans, poses a significant threat to livestock and the American economy.

A Dangerous Discovery

The US Department of Health and Human Services (HHS) and the Centers for Disease Control and Prevention (CDC) confirmed on August 4 that a resident of Maryland had been diagnosed with a New World screwworm infestation after traveling to El Salvador. This marks the first human case of the parasite, whose larvae are known to burrow into the living flesh of warm-blooded animals, to be identified in the US in over 50 years. Thankfully, the patient has fully recovered, and health officials say the risk to the public is “very low,” as the infection is not contagious and does not spread from person to person.

The Bigger Threat

While human cases are rare, the discovery is a major concern for the US cattle and livestock industry. The New World screwworm, so named because its larvae burrow into flesh with a screw-like motion, can kill a fully grown cow in as little as 10 days if left untreated. The USDA has previously estimated that a major outbreak could threaten over $100 billion of US economic activity tied to the livestock industry.

The USDA has been preparing for the possibility of screwworm re-entry for months, as outbreaks have been moving northward through Central America and Mexico. In response to this new case, the USDA has initiated targeted surveillance within a 20-mile radius of the affected area in Maryland, encompassing parts of Washington, D.C., and Virginia.

A Coordinated Response

The case highlights the importance of the Sterile Insect Technique (SIT), a biological control method that was used to eradicate the pest from the US in the 1960s. The USDA has recently announced plans to build a new sterile fly production facility in Texas, which will produce up to 300 million sterile flies per week to combat the pest if an outbreak were to occur. The sterile male flies are released into an area where they mate with wild female flies, who then lay unfertilized eggs, effectively breaking the pest’s breeding cycle.

Symptoms of a screwworm infestation can include severe pain, a foul odor, and visible maggots in or around an open wound. The condition requires immediate medical attention and treatment, which involves the surgical removal of the larvae from the affected tissue.