New World Screwworm Outbreak in Central America and Mexico
In 2023, NWS detections in Panama exploded from an average of 25 cases per year to more than 6,500 cases in 1 year. Since then, screwworm has been detected in Costa Rica, Nicaragua, Honduras, Guatemala, Belize, El Salvador, and Mexico, north of the biological barrier that's successfully contained this pest to South America for decades.
Establishing a New World Screwworm Sterile Fly Barrier Zone in Mexico
On Feb. 26, 2025, APHIS announced that we are shifting our sterile fly dispersal efforts to Mexico—the northernmost point of the outbreak. We have identified two locations in Mexico. As we transition to these sites, we will continue operations using dispersal centers outside of Mexico to ensure program continuity. APHIS remains committed to working closely with regional partners to support on-the-ground outbreak response activities, including surveillance, animal health outreach, and early detection efforts.
Current Status
Updated information on the current situation is available via the Panama-United States Commission for the Eradication and Prevention of Screwworm (COPEG) website.
Trade Restrictions
For a complete list of regions APHIS recognizes as affected by screwworm and any temporary trade restrictions, visit Animal Health Status of Regions. Detailed information about import requirements for all animal species regulated by APHIS is available at Live Animal Imports.
Eradicating Screwworm
APHIS is partnering with other USDA agencies, the U.S. Department of State, the Food and Agriculture Organization of the United Nations, and affected countries to respond to the outbreak. APHIS is investing $109.8 million to combat new NWS detections in Central America and Mexico to keep the pest from spreading into North America. With this funding, APHIS aims to eradicate NWS in Central America and Mexico and re-establish the biological barrier in the Darien Province.
The APHIS strategy to eradicate NWS in previously pest-free areas and re-establish the biological border in the Darien is rooted in three pillars known to be effective in combating this pest:
- Use of sterile insect technique
- Development and enforcement of animal movement controls
- Increasing passive and active surveillance, outreach, and education in impacted areas
APHIS maintains the only NWS pupae sterilization facility in North America. The facility is managed and funded jointly by USDA and Panama’s Ministry of Agriculture Development (MIDA) through COPEG.
Located in Pacora, Panama, COPEG produces, sterilizes, and releases NWS in the region. For maintenance of the biological barrier, the COPEG facility produces 20 million pupae with the capacity to increase to 100 million pupae per week during an outbreak, if required.
On Feb. 26, 2025, APHIS announced that it is shifting sterile fly dispersal efforts to Mexico—the northernmost point of the current outbreak. As we transition to these sites, we will continue operations using dispersal centers outside of Mexico to ensure program continuity. APHIS remains committed to working closely with regional partners to support on-the-ground outbreak response activities, including surveillance, animal health outreach, and early detection efforts.