Last Modified: March 04, 2026

New World screwworm (NWS) is a devastating pest. It can cause serious, often deadly damage to animals and people in areas where the pest spreads. While NWS is present in parts of South America—where infections in animals and people continue to occur—it was eradicated from the United States decades ago. In recent years, NWS has moved northward through Central America and Mexico. 

USDA is leading an aggressive national, One Health response to keep NWS out of our country.

NWS is not currently present in the United States.

Thanks to strong surveillance and response programs, the current risk to livestock, other animals, and people in the United States remains very low. Ongoing surveillance in animals shows no evidence of NWS in the United States.

Stopping the Spread

Our unified government approach spans multiple Federal agencies, in partnership with State, Tribal, local, and Territorial governments and industry. Together, we are taking bold action to stop the screwworm's northward spread in Central America and Mexico and protect the U.S. livestock industry, economy, food supply, and public health.
Current Status
Cluster of screwworm flies
What You Need To Know
A man and women looking at paperwork with cows in the background
Report a Suspect Case

U.S. Readiness

Planning and preparing for an outbreak of NWS is essential to protect public health, animal health, agriculture, the environment, our food supply, and the economy. 

With the support of industry, State, and Tribal partners, the United States remains vigilant against and fully prepared for possible screwworm incursions. As part of our five-pronged plan to defeat screwworm, we are supporting robust response activities in Mexico and Central America to push the pest back, and we have teams in place along the U.S. border to bolster our defenses and stay ahead of it. If screwworm crosses into the United States, we are ready to act quickly and aggressively to eliminate it.

Learn More About NWS Emergency Planning and Preparedness

Mass production and targeted dispersal of sterile flies remain critical components of our effective response. 

Sterile flies are one of the most important tools we have for eradicating screwworm. USDA is investing heavily in new and existing sterile fly infrastructure to ramp up production and expand our domestic response capacity. 

With these investments, production will approach approximately 500 million sterile flies per week—the same amount we used to eradicate NWS from the United States decades ago.

Track Status of Sterile Fly Production and Dispersal Facilities

Screwworm is not currently present in the United States—and we intend to keep it that way. 

USDA has intensive surveillance and monitoring systems in place along the U.S.-Mexico border to detect screwworm. We also have strict trapping, surveillance, and movement protocols established in Mexico, and we work closely with our counterparts there to ensure the protocols are followed.

Learn More About Surveillance

Across the Federal Government, we're driving innovation to win the fight against screwworm. 

Science and collaboration are critical to our success. USDA has announced the NWS Grand Challenge. This funding opportunity makes up to $100 million available to support innovative projects that enhance sterile NWS fly production, strengthen preparedness and response strategies, and safeguard U.S. agriculture, animal health, and trade.

We're also pursuing extensive research to bolster our response strategies and ensure we have all the tools we need to detect, control, and eliminate this pest. 

Learn More About Innovation and Research

The U.S. Government is using all resources at our disposal to stop screwworm.

USDA has established a dedicated New World Screwworm Directorate within APHIS focused on coordinating and implementing the Secretary’s plans. We are collaborating closely with the U.S. Centers for Disease Control and Prevention, U.S. Department of the Interior, and numerous other agencies to ensure a unified Federal response.

Learn More About Federal Coordination

What You Need To Know

Livestock Producers
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Veterinarians
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Animal Health Officials
Wildlife Professionals
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Healthcare Providers
Public Health Officials
Drug Manufacturers
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Researchers
Travelers
Pet Owners
Hunters
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General Public

Report Suspected Cases of Screwworm

Contact your veterinarian right away if you see any suspicious wounds, maggots, or infestations in your animals or herd. Animal health professionals report suspected cases to the State animal health official and APHIS Area Veterinarian in Charge. 

Contact your healthcare provider if you think you may have screwworm. Healthcare providers report suspected cases to the local or State health department.