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Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Repair Windows errors before they cause bigger problemsFix Now →U.S. health and agriculture officials confirmed the nation’s first reported human case of New World screwworm (Cochliomyia hominivorax) in August 2025. The infection was travel-associated, not acquired in the United States: CDC says the traveler had returned from El Salvador, and CDC reports no human cases acquired locally in the country. CDC currently assesses the U.S. public-health and animal risk as very low, but a suspected infection requires immediate medical, veterinary and public-health notification.
What U.S. officials confirmed
The Maryland Department of Health and CDC confirmed the infection on August 4, 2025. USDA announced the travel-associated case on August 26. CDC’s current situation summary identifies El Salvador as the traveler’s destination.
Some early secondary reports cited Guatemala. Reuters reported that industry sources had mentioned Guatemala, while HHS spokesperson Andrew G. Nixon identified El Salvador. The official CDC/HHS attribution is El Salvador; the conflicting early report has not been resolved publicly.
| Date | Development |
|---|---|
| August 4, 2025 | Maryland health officials and CDC confirmed the human infection. |
| August 25, 2025 | HHS spokesperson Andrew G. Nixon said the U.S. public-health risk from the introduction was “very low,” as quoted by Reuters. |
| August 26, 2025 | USDA announced the travel-associated U.S. case. |
What New World screwworm is
New World screwworm (NWS) is a parasitic fly whose larvae feed on living tissue. A female lays eggs in a wound or body opening; the larvae then develop in the tissue. The parasite can infest people, livestock, pets and wildlife.
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Unlike an incidental finding of insects around a wound, NWS causes obligate myiasis—the larvae must feed in living tissue. Untreated infestations can destroy tissue and may be fatal in animals.
Was the U.S. case locally acquired?
No. CDC describes the 2025 infection as travel-associated and says there have been no reports of a human NWS infestation acquired in the United States.
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USDA’s July 1, 2026 status page lists animal NWS detections in the United States. Those later animal detections are a separate development from the 2025 human case and do not establish that the Maryland traveler was infected domestically. CDC continued to report no locally acquired human infestations.
How large is the regional outbreak?
USDA says the outbreak moved north after the barrier zone in eastern Panama was breached, spreading through Central America toward Mexico beginning in 2023. The agency describes NWS as a major livestock threat and uses surveillance, trapping, animal-movement controls and sterile-fly releases to contain it.
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- BUG KILLER - Our product controls horn flies, face flies, house flies, horse flies, fruit flies, stable flies, & deer flies. It also controls species of mosquito, gnat, poultry lice, mite, flea, tick, cockroach, spider, cricket, ant, & more.
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In an August 11, 2026 update, CDC reported more than 209,400 animal cases and more than 2,600 human cases in Central American countries and Mexico. Those are CDC’s published cumulative totals as of that date, not a U.S. case count.
What risk does this pose to people and pets in the United States?
CDC’s current assessment places the U.S. public-health and animal risk at very low. The practical distinction is important:
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| Situation | What is established |
|---|---|
| 2025 Maryland human case | Travel-associated; official CDC/HHS reporting identifies travel to El Salvador. |
| Human infection acquired in the U.S. | CDC reports no locally acquired human cases. |
| U.S. animal detections in 2026 | Listed by USDA; these are separate from the 2025 human case. |
| Pets as potential hosts | Pets can develop infestations if larvae reach a wound or body opening. |
A human infestation can also alert officials to an infested animal or an established fly population. That is why rapid reporting matters even when overall risk is low.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Signs owners and travelers should recognize
In people
- A wound or sore that becomes increasingly painful or worsens instead of healing
- Foul odor or bleeding from the wound
- Visible maggots or a sensation of movement in the wound
Anyone returning from an affected area who develops these signs should seek prompt medical evaluation and tell the clinician about recent travel. Suspected human cases should be reported immediately to the local or state health department.
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In pets
NWS can affect pets and other warm-blooded animals. A worsening, foul-smelling or bleeding wound, or visible larvae, warrants an urgent veterinary examination—especially after travel or exposure in an outbreak-affected region. Do not wait to see whether the wound improves.
How suspected infestations are treated
CDC clinical guidance says treatment requires physical extraction of all larvae by a clinician. Suspected human cases must be reported immediately. CDC notes only anecdotal reports for ivermectin and no controlled double-blind studies measuring its effect for NWS myiasis, so medication decisions belong to a treating professional.
Do not try to remove larvae with household chemicals, insecticides or consumer wound products, and do not use ivermectin as a self-treatment. For a pet, contact a veterinarian immediately; the veterinarian and animal-health authorities can coordinate testing, removal and reporting.
How officials are responding
USDA’s response combines detection and prevention: surveillance of animals and flies, trapping, movement controls and sterile-fly methods. The eastern-Panama barrier is intended to slow northward spread, while rapid notification of suspected human or animal cases helps officials investigate possible transmission.
What pet owners should do now
- Check any wound or sore that is worsening, bleeding or producing a foul odor.
- Look for visible larvae and seek urgent veterinary care rather than attempting home removal.
- Tell the veterinarian about travel or animal movement through Central America, Mexico or other affected areas.
- For a person with compatible symptoms after travel, obtain medical care immediately and notify the local or state health department.
- Follow instructions from public-health, veterinary and USDA animal-health officials if a case is suspected.
The 2025 Maryland case demonstrates that travelers can bring NWS infections back to the United States, but it was not locally acquired. The later U.S. animal detections make surveillance especially important for veterinarians and owners, while CDC’s reported human status remains unchanged: no locally acquired human cases.
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