A parasitic fly whose larvae burrow into living flesh within hours of hatching has been confirmed in southern Texas, and on June 16, 2026, the U.S. Centers for Disease Control and Prevention activated a Level 3 Emergency Operations Center to coordinate the federal response.
According to HealthDay, the CDC is supporting the USDA and Texas Department of State Health Services after the parasitic infestation — New World screwworm — was found in domestic animals in southern Texas and one county in New Mexico. As of June 11, 2026, the USDA confirmed 12 cases in livestock, including sheep, cattle, and goats.
No human cases have been confirmed in the United States. The CDC assesses the current public risk as low. But the agency is explicit: New World screwworm can infest people, and clinicians in affected areas must stay alert.
What New World Screwworm Is — and Why It Demands Attention Now
New World screwworm (NWS) is caused by the larvae of Cochliomyia hominivorax, a parasitic fly that feeds exclusively on living flesh. Unlike many parasites that feed on dead tissue, NWS larvae burrow into living muscle and organs — a characteristic that makes infestations rapidly destructive.
According to the CDC, NWS occurs when flies lay eggs in wounds or body openings, including the ears, nose, genitals, and the navel of newborns. The eggs hatch within hours, and the maggots burrow into living tissue, causing myiasis. Without treatment, severe infestations can be fatal.
The United States previously eradicated NWS domestically through the USDA's sterile insect technique program. The current detection represents the first confirmed domestic animal cases since that eradication. USDA reports the first case was confirmed June 3, 2026, in a 3-week-old calf in Zavala County, Texas.
On June 16, the FDA also issued an emergency use authorization for generic nitenpyram tablets — the first generic animal drug authorized against NWS — for dogs, puppies, cats, and kittens.
| New World Screwworm Key Data (as of June 16, 2026) | Detail |
| CDC EOC level activated | Level 3 |
| First U.S. animal case | June 3, 2026, Zavala County, Texas |
| U.S. animal cases (as of June 11) | 12 (sheep, cattle, goats) |
| States with confirmed animal cases | Southern Texas; 1 county in New Mexico |
| U.S. human cases | 0 |
| Public risk (CDC assessment) | Low |
| Mexico/Central America animal cases since 2023 | 185,000+ cumulative |
| Mexico/Central America human cases since 2023 | 2,100+ |
| Prior U.S. travel-associated human case | 1 (August 2025, from El Salvador) |
| FDA action June 16 | Emergency use authorization: generic nitenpyram for pets |
| Spread route | Does NOT spread animal-to-animal, animal-to-human, or person-to-person |
The Regional and International Context
The resurgence began in Panama and Costa Rica in 2023. Since then, NWS has re-established across all previously controlled Central American countries and Mexico, producing 185,000+ animal cases and 2,100+ human cases. The June 3 confirmation of NWS in a Texas domestic calf represents locally acquired animal infection, escalating the situation beyond travel-associated cases.
"CDC is just one more step in the right direction that allows us to deploy more resources at the federal level," USDA Secretary Brooke Rollins said at a Texas press briefing, according to reporting on the CDC activation.
A critical distinction: the CDC states NWS "cannot spread from animal to animal, animal to people, or person to person." Infestation only occurs when a NWS fly lays eggs directly in a wound or opening. Physical proximity to an infested animal does not confer risk.
Who Is Most At Risk — and What Providers Must Do
Livestock workers and ranchers in southern Texas and New Mexico face the highest practical risk through occupational exposure around animal wounds. Pet owners should check animals regularly for unusual wound activity or larvae. Healthcare providers in affected areas are being directly asked by the CDC to watch for signs of human myiasis, particularly in patients with unusual wound pain or swelling following outdoor exposure.
Any suspected human case should be reported to local or state health departments immediately. Clinicians can contact the CDC at dpdx@cdc.gov or 404-718-4745 for diagnostic assistance. After-hours inquiries go to the CDC Emergency Operations Center at 770-488-7100.
The USDA's screwworm.gov coordinates the interagency response — co-led by USDA, CDC, and the Department of the Interior. "The United States has defeated New World screwworm before — together, we will do it again," the USDA stated.
Frequently Asked Questions
What is New World screwworm, and why is it dangerous?
Caused by Cochliomyia hominivorax larvae, NWS feeds exclusively on living tissue, unlike most parasites. Infestations develop rapidly in wounds and body openings, can worsen quickly, and can be fatal without treatment in both animals and humans.
Are humans at risk in Texas?
The CDC assesses the current public risk as low, with no confirmed U.S. human cases. However, human infestation is biologically possible if a NWS fly lays eggs in an open wound. Livestock workers and people with open wounds in southern Texas and New Mexico face the highest practical risk.
Can NWS spread from animals to people?
No. NWS cannot spread animal-to-animal, animal-to-person, or person-to-person. Infestation only occurs through direct fly contact with a wound or body opening.
What should I do if I think I or a pet has been infested?
For pets, contact a veterinarian immediately — generic nitenpyram is now FDA-authorized. For humans, seek emergency care and contact your state health department. Providers can reach the CDC at dpdx@cdc.gov.
Has the U.S. dealt with NWS before?
Yes. The U.S. eradicated NWS in the 1960s–1970s through the USDA sterile insect program, which is now being redeployed.
