First U.S. human case of New World screwworm confirmed in Maryland—public health risk low, surveillance underway. Learn latest updates.

Key Points Summary

• A human case of New World screwworm myiasis was confirmed in Maryland, linked to recent travel to El Salvador. (Reuters)
• The U.S. Department of Health and Human Services (HHS), the CDC, and Maryland health officials say there is no spread to others or animals. (HHS.gov)
• Risk to public health and livestock in the U.S. is assessed as very low for now. (Reuters)
• USDA is enhancing surveillance along the U.S.–Mexico border, planning for a sterile fly facility to help contain the threat. (Reuters)
• The New World screwworm fly (Cochliomyia hominivorax) is making a northward comeback, prompting concerns in agriculture and health sectors. (Reuters)

What Happened

On August 4, 2025, U.S. public health authorities confirmed a rare case of travel-associated New World screwworm in a patient who recently returned to Maryland from El Salvador. The Centers for Disease Control and Prevention (CDC), in coordination with Maryland’s Department of Health, verified the case of New World screwworm myiasis. (HHS.gov)

Health officials stress that this is not a domestic outbreak: there is no evidence of the parasite spreading to other people or animals within the U.S. (HHS.gov)

What Is New World Screwworm

New World screwworm, scientifically Cochliomyia hominivorax, is a parasitic fly whose larvae feed on living flesh. It lays eggs in wounds or body openings (ears, nose, etc.), then larvae hatch and begin burrowing into tissue. This causes serious damage (myiasis), and without timely treatment, can become life-threatening. (CDC)

Historically, the U.S. eradicated New World screwworm in the mid-20th century through the sterile insect technique—mass releasing sterilized male flies to interrupt reproduction. It remained largely absent until recent resurgence in Central America and southern Mexico. (Wikipedia)

Significance & Risk Assessment

Although this is the first confirmed human case of New World screwworm in decades in the U.S., experts say the public health risk is very low. (HHS.gov)

• There are no reported cases in U.S. livestock or wildlife at present. (HHS.gov)
• Officials have confirmed no sign of transmission beyond the individual. (HHS.gov)

Response from Authorities

In light of the case, U.S. authorities have taken steps to strengthen detection and prevention:

• HHS, CDC, and USDA are carrying out proactive surveillance in the region around the patient’s location (Maryland, D.C., Virginia). (HHS.gov)
• USDA is working on a multi-part plan, including building a sterile fly facility, border trap networks, and coordination with Mexico to limit the northward spread of New World screwworm. (Reuters)
• Livestock import restrictions have been used previously (e.g. Mexican cattle) to reduce risk of spread. (Reuters)

Economic & Agricultural Concerns

For the agriculture sector, the potential costs are significant if New World screwworm becomes established in livestock populations. Estimates for outbreaks (e.g. in Texas) run into billions of dollars owing to death of animals, treatment costs, labor, and lost trade. (Reuters)

Treatment & Clinical Notes

In human cases, treatment involves surgical removal of larvae, cleaning of wounds, and antibiotic treatment to prevent secondary infection. With prompt medical care, recovery is possible. (CDC) People with wounds, immunocompromised individuals, or those traveling from outbreak regions are at higher risk. Vigilance and early detection matter. (CDC)

Comparative Review & Context

Sources

• Information sourced from official U.S. government agencies: HHS, CDC, USDA. (HHS.gov)
• Peer-reviewed scientific data on screwworm biology and eradication history. (researchgate.net)
• Supporting media and farm/agriculture policy outlets confirming economic stakes. (Reuters)

While this is U.S.-based news, farmers, veterinarians, and public health workers along the Mexico border are especially affected. In addition, global supply chains for beef and livestock trade may also feel reverberations if New World screwworm spreads. Communities with frequent travel to outbreak zones (Central America) face elevated personal risk.

Transparency & Trust

• All claims backed by government releases and trusted outlets. (HHS.gov)
• Uncertainties are clearly stated, e.g. origin country discrepancies, lack of animal cases.
• Privacy respected: details about patient identity withheld.

What to Watch Going Forward

• Whether any New World screwworm cases emerge in animals in the U.S., especially near border areas.
• Completion and operational date for the new sterile fly production facility.
• Effectiveness of surveillance and border / import restrictions.
• Updates from CDC and USDA on trapping results and new case investigations.

FAQ

What happened in the New World screwworm case?
A U.S. resident in Maryland, returning from El Salvador, was confirmed to have New World screwworm myiasis. The case was verified by CDC and local health authorities. (HHS.gov)

Why is New World screwworm important?
Because it is a parasitic fly that can devastate livestock, wildlife, and in rare cases humans. Its presence threatens agriculture, food safety, and public health. (CDC)

How does New World screwworm affect people and animals?
Infection in animals often leads to severe tissue damage, economic loss, and death if untreated. In humans, myiasis can be painful and dangerous, but treatment is effective when applied early. (CDC)

What are the latest updates on New World screwworm?

• Human case confirmed in Maryland. (HHS.gov)
• No animal cases in the U.S. so far. (HHS.gov)
• USDA developing sterile fly facility; increasing surveillance. (APHIS)

Where can I read more about New World screwworm?

• CDC’s clinical overview page on New World screwworm. (CDC)
• USDA / APHIS website updates on livestock disease control. (APHIS)
• Reuters and other reputable news outlets reporting on outbreak developments. (Reuters)

On A Positive Note

While the resurgence of New World screwworm is unsettling, the quick detection of this human case, coordinated response by U.S. health authorities, and existing scientific tools for containment show that the situation remains under control. If surveillance and prevention strategies—like the sterile fly technique—are successfully scaled up, the damage can be contained well before any widespread impact occurs. For now, the emphasis is on vigilance, preparedness, and cross-border cooperation, which gives reason to believe that this challenge can be met effectively.

Disclaimer:

This article is for informational purposes only and is not a substitute for medical advice. Always consult a healthcare professional.

Jo Parr is a lifestyle and health writer passionate about making complex topics simple, relatable, and inspiring. With a forward-thinking approach, Jo creates content that empowers readers to make confident choices for a healthier, more meaningful life.