The risk of New World screwworm infestation for humans in the United States remains very low, according to the Centers for Disease Control and Prevention (CDC), following the first confirmed case in domestic animals on June 3, 2026. While the parasite has caused widespread issues in Mexico and Central America, health officials report no locally acquired human infestations in the U.S. as of Aug. 20, 2026.
Regional Impact and U.S. Status
The New World screwworm, a fly whose larvae burrow into the living tissue of warm-blooded animals, was first detected in a U.S. animal on June 3, 2026, according to the USDA-APHIS. This marks a significant development for a parasite that was previously considered eradicated in the United States since 1968.
While the United States has seen animal cases, the impact in other regions remains much higher. The CDC reported on Aug. 20, 2026, that more than 209,400 animal cases and 2,500 human cases have been recorded in Mexico and Central American countries. This resurgence follows an outbreak in Panama and Costa Rica identified in 2023, which eventually spread through Central America and Mexico to include livestock, pets, and wildlife.
In the United States, the CDC has reported no instances of human infestations acquired locally. However, individuals may face a higher risk if they live in areas where screwworm flies have infested animals or if they travel to areas where the parasite is active.
Economic and Management Risks
The Utah Department of Agriculture and Food (UDAF) has been tracking the implications of the parasite. On July 27, 2026, the department noted that there were currently no movement restrictions or additional instructions for Utah producers regarding the screwworm.
UDAF Commissioner Kelly Pehrson and State Veterinarian Dr. Amanda Price, DVM MS, have discussed the implications of the New World screwworm for the region. The department maintains that if the screwworm is reintroduced to the United States, it could result in costs reaching billions of dollars due to treatment expenses, production losses, and animal deaths.
To manage the threat, the USDA is working in coordination with Mexico to attempt to stop the spread before it reaches the southern border. The response strategy led by the USDA includes several key measures: the release of sterile insects, intensive surveillance, controls on animal movement, and educational outreach programs in affected areas.
Public Health Response
The CDC is currently monitoring the outbreak using a "One Health" approach, collaborating with the USDA, the Department of the Interior (DOI), and various federal, state, local, and tribal partners to prevent further spread among humans and animals.
Medical professionals are advised to be vigilant. The CDC notes that if a healthcare provider suspects a New World screwworm infestation, they must immediately notify local or state health departments. Veterinarians are similarly required to report any suspicious cases in animals to state animal health officials and the USDA-APHIS office.
For individuals, the CDC recommends keeping any open wounds clean and covered, regardless of size. To limit skin exposure, the agency suggests wearing long-sleeved shirts, loose-fitting long pants, hats, and socks. Using EPA-registered insect repellents and treating clothing or equipment with 0.5% permetrine are also recommended protective measures.
Symptom Identification and Reporting
Identifying the symptoms of an infestation is critical for both human and animal health. In humans, symptoms can include painful skin lesions or sores that lack an apparent cause and do not heal. Other indicators include an unpleasant odor or bleeding at the site of the infestation. In some cases, individuals may see or feel larvae moving within open wounds or in sensitive areas such as the nose, mouth, eyes, ears, or genitals.
The CDC warns that if larvae are seen or felt in a wound, individuals should seek medical attention immediately. Medical providers may need to perform a procedure to extract all larvae. The agency strongly advises against attempting to extract or remove the larvae manually.
For animal owners, the Utah Department of Agriculture and Food provides resources to help distinguish the New World screwworm from other issues like Cuterebra (botflies). The department encourages anyone suspecting a case in Utah to use official submission forms to report the incident to the State Veterinarian’s office.
Ongoing Monitoring
As the situation evolves, the CDC and USDA continue to update information via screwworm.gov. The agency emphasizes that while the current risk to the U.S. public and animals is very low, the historical presence of the fly in the U.S. and its recent resurgence in neighboring countries necessitate continued vigilance and reporting from both veterinarians and the general public.
Background on the Parasite
The New World screwworm is a fly that causes larvae to burrow into the living tissue of warm-blooded animals. This process creates large wounds and can lead to death in untreated animals. The parasite's ability to target both livestock and pets makes it a significant concern for agricultural stability and animal welfare.
