New World Screwworm Outbreak Moves into Northern Mexico

Kansas Health Alert Network (KS-HAN) Posted on January 23, 2026

Summary

The Centers for Disease Control and Prevention (CDC) issued Health Advisory No. 526 on January 20, 2026, to inform clinicians, public health, and the public about recent New World screwworm (NWS) animal cases in the Mexican state of Tamaulipas, which shares a border with the U.S. state of Texas. No recent NWS infestations related to this outbreak have been identified in people or animals in the United States as of January 20, 2026. However, given the potential for geographic spread, CDC and the Kansas Department of Health and Environment (KHDE) are issuing this alert. The purpose of this alert is to increase awareness of the outbreak and to summarize public health recommendations for healthcare providers and local health departments regarding case identification and reporting, specimen collection, diagnosis, and treatment of NWS, as well as provide guidance for the public.

While NWS remains primarily an animal health issue, humans can become infected with NWS when they have an open wound or bleeding from mucous membranes. The primary threat to U.S. residents is travel to an endemic or outbreak area, such as Central America and Mexico. Healthcare providers should be aware of the possibility of travel-associated cases.

Mandated Reporters, including clinicians, are required by Kansas Administrative Regulation ( K.A.R. 28-1-2 ) to report by phone all suspected cases of NWS human infestations to the 24/7 KDHE Epidemiology Hotline (877-427-7317, option 5) within four (4) hours of suspicion to facilitate rapid investigation, sample identification and submission, and treatment guidance.

New World Screwworm Background

New World screwworm (NWS) is a devastating pest. NWS myiasis (parasitic infestations) occurs when NWS flies lay eggs in wounds or in other body cavities with mucus membranes, such as the nose, ears, eyes, or mouth. The eggs develop into parasitic larvae (maggots) that feed on and burrow into living flesh. Although they primarily affect livestock, such as cattle and horses, the flies can also lay eggs on people and other warm-blooded animals, both domestic and wildlife. Cases of NWS in people can be fatal if left untreated.

An outbreak of NWS infestations in people and animals has developed across Central America and Mexico. During this outbreak, more than 1,190 cases and seven deaths in people have been reported in Central America and Mexico as of January 20, 2026. The Mexican state of Tamaulipas, which borders the U.S. state of Texas, reported eight active animal cases. The NWS fly has not been detected in the United States and the risk to people remains low.

People might be at an increased risk for NWS if they spend time in geographic areas where the NWS flies are present and if they have or do any of the following:

• An open wound, including scratches, cuts, insect bites, or surgical wounds
• A weakened immune system, including from HIV, cancer treatment, or medications that weaken the immune system
• A medical condition that can cause bleeding or open sores, such as skin cancer or sinus cancer
• People who are very old or very young
• People experiencing malnutrition
• People who sleep outdoors, especially during daytime hours when NWS flies are more active
• People who live, work, or spend an extended amount of time near livestock or other warm-blooded animals in these areas Recommendations for Healthcare Providers

Immediately report all suspected human cases to the 24/7 KDHE Epidemiology Hotline at (877) 427-7317, option 5 to seek confirmatory diagnosis with the CDC’s Diagnostic Parasitology Lab and for clinical inquiries and patient management-related questions. Healthcare providers should consider NWS in people with recent travel to regions with NWS activity who present with visible larvae or egg masses in a wound, ears, eyes, nose, mouth, or other body orifice, destruction of healthy tissue, or sensation of movement, foul odor, bloody discharge, swelling, and pain.

For patients with larval infestations in a lesion, providers should follow instructions from the KDHE Epidemiology Hotline on larvae submission for confirmation at CDC. Promptly remove all larvae and eggs from patients with suspected NWS and place them in 70% ethanol, which will kill the larvae and preserve them for identification. This will require physical removal of all larvae. Failure to kill and properly dispose of all larvae or eggs could result in the new introduction and spread of NWS in the local environment.

• Place at least 10 larvae in a leak-proof container containing a volume of liquid sufficient to fully submerge larvae for identification. If multiple stages of larvae are present in the lesion, try to include a representative sample from each stage.
• 70% ethanol (preferred) will both kill and preserve the larvae and eggs for identification. Alternative liquids include 70% or greater isopropanol, or if no alcohol is available, 5-10% formalin is acceptable.
• Collect any remaining larvae and eggs in a separate leakproof container, submerge them in alcohol, place the container into a zip-top plastic bag, and seal it. Dispose of the sealed bag in the trash. The treatment of NWS in humans is removal of all eggs and larvae, which might require surgical extraction if the larvae are embedded deeply into the tissues. There have not been any studies to prove that any specific medication, including ivermectin, is useful in treatment in humans. Patients with secondary infections or additional symptoms may need supportive care. Reexamine treated lesions after 24-48 hours to confirm no live larvae remain. Remove and safely dispose of any remaining larvae as described above.

Recommendations for Local Health Departments

Local health departments are advised to take the following actions. Your proactive response and collaboration are vital to protecting public health in Kansas.

• Share this alert with healthcare providers, hospitals, and clinics in your county to ensure they are informed and prepared.
• Promptly report any suspected case of human NWS infestations to the KDHE Epidemiology Hotline at (877) 427-7317, option 5. **** Encourage mandated reporters in your area to do the same.
• Promptly report any suspected case of animal NWS infestations to the Kansas Department of Agriculture Division of Animal Health at (785) 564-6601.
• The KDHE Infectious Disease Epidemiology & Response team will lead public health investigations of human cases. Relevant case details will be shared with your health department through the KS EpiTrax system to support coordination.
• For any questions, or further clarification, please reach out to the KDHE Epidemiology Hotline at [email protected] or your regional field epidemiologist. Recommendations for the Public

The NWS fly has not been detected in the United States and the risk to Kansans remains low. Prevention is key to protecting yourself. Travelers to areas where NWS flies are present can prevent infections by following insect bite precautions when traveling, plus keeping any open wounds clean and covered, no matter how small or where they occur on the body. Travelers should wear loose-fitting, long-sleeved shirts and pants, socks, and hats to limit areas where you could get bitten. Use an EPA-registered insect repellent on exposed skin and treat clothing and gear with 0.5% permethrin. Sleep indoors; if the room has windows, the windows should be screened. If you are outside, sleep under a bed net or inside a screened tent.

If you see or feel maggots (larvae) in or on a wound or other area of your body, seek medical care immediately. Do not try to remove any maggots or egg masses yourself. Do not throw any maggots or eggs in the trash or outside on the ground. This could result in NWS spreading in your area. If maggots or eggs fall out of the wound, cover them with alcohol (70% ethanol) in a leak-proof container and bring them to a healthcare provider. Contact your local health department or healthcare provider if you have questions about NWS.

Resources

• For more information on NWS and the unified government approach to protect the United States: www.screwworm.gov
• To report potential human cases of NWS, call the KDHE Epidemiology Hotline at 1-877-427-7317, option 5.
• For general questions or further clarification on NWS in humans, please reach out to the KDHE Epidemiology Hotline at [email protected].
• To report suspect cases in animals, please reach out to the Kansas Department of Agriculture immediately at 785-564-6601. NWS in animals is a reportable condition and must be reported to the KDA Division of Animal Health.

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