First Travel-Associated Case of Flesh-Eating Parasite Confirmed in the US

On August 25, 2025, the U.S. Department of Health and Human Services (HHS) confirmed the first human case of New World screwworm (NWS), a flesh-eating parasite, in Maryland. The case, identified in a traveler returning from El Salvador, was verified by the Centers for Disease Control and Prevention (CDC) and the Maryland Health Department on August 4. This marks the first travel-associated case of New World screwworm myiasis, a condition caused by the parasite’s larvae infesting living tissue, in the United States. Authorities have emphasized that the risk to public health remains very low, and the patient has fully recovered with no evidence of transmission to other people or animals.

Understanding New World Screwworm

New World screwworm (Cochliomyia hominivorax) is a parasitic fly primarily known for affecting livestock but capable of infesting humans. The female fly lays eggs in open wounds or body openings, such as the nose, mouth, or eyes. Once hatched, the larvae, or maggots, burrow into living tissue, feeding in a way that resembles a screw’s motion, which gives the parasite its name. If untreated, infestations can be painful and, in rare cases, fatal for both animals and humans. The CDC notes that infestations are treatable but require prompt medical attention to remove the larvae and disinfect affected areas.

How the Parasite Spreads

The New World screwworm does not typically spread from person to person or occur naturally in the U.S. It is more common in South America and the Caribbean, where flies lay eggs in open wounds of warm-blooded animals, including livestock, wildlife, pets, and, rarely, humans. The Maryland case was linked to travel to El Salvador, an outbreak-affected region. The investigation confirmed no local transmission, meaning the parasite has not spread to others in the U.S. from this case.

Who Is at Risk?

While the risk of New World screwworm in the U.S. is minimal, certain factors increase vulnerability:

• Traveling to regions where the parasite is common, such as South America or the Caribbean.
• Spending time around livestock in affected areas.
• Sleeping outdoors, especially with open wounds.
• Having a weakened immune system, which may worsen the effects of an infestation.

These conditions make individuals more susceptible to the parasite, particularly if they have untreated wounds that attract female flies.

Symptoms of New World Screwworm Myiasis

An infestation, known as myiasis, is often very painful and requires immediate medical attention. According to the CDC, symptoms to watch for include:

• Unexplained skin lesions or sores that do not heal.
• Worsening skin wounds or sores over time.
• Pain or discomfort in affected areas.
• Bleeding from open sores.
• Sensation of larvae moving within a wound, nose, mouth, or eyes.
• Visible maggots in or around open sores.
• Foul odor from the infested area.
• Secondary bacterial infections, which may cause fever or chills.

If you notice these symptoms, especially after traveling to an affected region, contact a healthcare provider immediately.

U.S. Efforts to Combat the Parasite

Although the human health risk is low, New World screwworm poses a significant threat to livestock, wildlife, and pets, potentially devastating cattle herds. To prevent its spread, U.S. Agriculture Secretary Brooke L. Rollins has outlined a five-part plan, including breeding and releasing sterile flies over southern Texas and Mexico. This strategy, which was successful in eradicating the parasite in the U.S. during the 1960s, involves releasing sterile male flies that mate with wild females, preventing viable offspring and reducing the parasite’s population. The U.S. has also implemented measures like suspending livestock imports from affected regions to protect the agriculture industry.

Staying Safe and Informed

The CDC assures that New World screwworm is not a widespread concern in the U.S., and the Maryland case appears isolated. Travelers to South America or the Caribbean should take precautions, such as protecting open wounds and avoiding outdoor sleeping in affected areas. If you suspect an infestation, seek medical help promptly to address symptoms and prevent complications. By staying informed and cautious, travelers can minimize risks while the U.S. continues efforts to keep this parasite at bay.

This article was written by Will and edited with AI assistance.