New World Screwworm Cases in the U.S. Reach 20, All But One in Texas as Medina County Joins Quarantine Zones

Since the first U.S. case on June 3 in a three-week-old Zavala County calf, the New World screwworm outbreak has expanded steadily across West and South Texas, reaching 20 confirmed animal cases as of the most recent reporting, according to FOX 7 Austin and the USDA's screwworm.gov portal.

Nineteen of the twenty cases are in Texas. The most recent wave included three detections in Terrell County cattle on June 23, following a Terrell County goat confirmed on June 22. The newest geographic expansion hit Medina County, prompting Texas Animal Health Commission Executive Director Dr. Lewis R. Dinges to sign an executive order on June 24 officially establishing "Infested Zone 09." That order imposes strict movement restrictions across parts of Bandera, Medina, and Uvalde counties.

What the Quarantine Actually Means

Under the orders signed by Dr. Dinges, no warm-blooded animal inside a designated infested zone can be moved outside without prior state authorization. Hides, carcasses, and animal parts that could host the parasite are also barred from leaving quarantine areas until inspected, treated, and cleared by a Texas Animal Health Commission representative. Unauthorized movement carries both administrative penalties and the possibility of criminal prosecution, according to FOX 7 Austin.

Ranchers seeking to move animals must contact TAHC to schedule a physical inspection. An animal health official then issues an official movement certificate documenting the treatments applied and the animals' identification tags.

Texas was not caught flat-footed. Governor Greg Abbott issued a statewide disaster proclamation about the screwworm threat as early as January 29, 2026, renewing it monthly. He issued an updated proclamation on June 5, two days after the first physical detection.

The Scale of What Texas Is Up Against

Mexico, where the pest resurged sharply, has reported more than 29,000 cases since November 2024, with roughly 1,800 currently active, according to FOX 7 Austin. The southward pressure on the U.S. border has been relentless. Tom Paterson, president of the New Mexico Cattle Growers' Association and a Catron County rancher, told The Guardian that earlier this year the industry stopped asking whether screwworm would arrive and started advising members on what to do when it did.

The USDA's screwworm.gov (last modified June 24) says production of sterile flies will approach approximately 500 million per week, the same volume used to eradicate the pest from the U.S. decades ago. USDA has also announced a "NWS Grand Challenge" with up to $100 million in available funding for new approaches. The agency describes protecting livestock and wildlife from screwworm as "a national security priority."

The Human Risk Nobody Is Talking About Enough

The USDA and Texas officials have been consistent: the current risk to people is described as very low, no human cases have been reported, and the U.S. food supply is not affected. That framing is accurate as far as it goes.

But The Guardian raises a concern that warrants consideration. Agricultural workers, the people most likely to encounter the parasite in real daily conditions, often work hours that run past clinic closing times, live on remote work sites, lack health insurance, and face language barriers. Rebekah Stewart, a clinical educator and care coordinator with the Migrant Clinicians Network and a family nurse practitioner, told The Guardian: "If they're not in touch with the healthcare system, they're very likely not going to be picked up by any of the surveillance that is being done."

Stewart's point is a legitimate public health concern, not partisan spin. Surveillance systems catch what gets reported. Workers who never see a doctor are invisible to outbreak monitoring. That gap is real regardless of immigration politics.

The Guardian's framing does veer into advocacy at points, folding in H5N1 bird flu comparisons and Trump administration immigration enforcement as compounding fears. Some of that contextualizing goes beyond what the screwworm data alone supports. But the underlying structural point — that remote agricultural workers are a surveillance blind spot — reflects a genuine monitoring vulnerability.

What Happens Next

Multiple infested zones now span parts of South and West Texas. TAHC and Texas Parks and Wildlife are updating situation reports daily as new inspections occur, according to FOX 7 Austin. The USDA's sterile fly program remains the primary eradication tool, but the agency has not published a timeline for when sterile fly dispersal will reach full operational capacity at the 500-million-per-week target.

The unresolved question as of June 26: whether the Medina County detection represents screwworm pushing northeast toward more densely populated ranch country, or whether it is an isolated focal point that containment can hold. Dr. Dinges and TAHC have committed to daily updates, but the geographic pattern of the last three weeks — steady county-by-county expansion — has not yet shown a clear sign of slowing.