Maryland confirms human case of New World screwworm

August 27, 2025

Staff Report

A medical milestone has been recorded in the United States as health officials confirm the first travel-associated human case of New World screwworm (NWS) myiasis in more than half a century. The diagnosis was confirmed on Aug. 4, 2025, and occurred in a Maryland resident recently returned from travel to El Salvador.1

New World screwworm, scientifically known as Cochliomyia hominivorax, is a parasitic blowfly whose larvae feed on living tissue, often infesting open wounds or body orifices such as the nose, eyes, or mouth. While primarily a threat to livestock, human cases, though rare, can be excruciatingly painful and pose serious health risks if untreated.2

The Case in Maryland

The case involved a Maryland resident with recent travel history to El Salvador. The Centers for Disease Control and Prevention (CDC) confirmed the infestation on August 4, working with the Maryland Department of Health. The individual has recovered.3

Officials stress that the risk to the general public remains very low. Screwworm is not contagious between people, and infections are typically linked to exposure in regions where the parasite is endemic.4

Response Measures and Prevention

As NWS steadily spreads northward through Central America and southern Mexico, U.S. authorities are ramping up proactive prevention and control measures:

The U.S. Department of Agriculture (USDA) is reviving the sterile insect technique, releasing mass-produced sterile male flies to disrupt reproduction, mirroring the successful eradication strategies of the 1950s and 1960s.5

Plans are underway to build a sterile fly production facility in South Texas, capable of yielding hundreds of millions of sterile flies weekly.6

Emergency declarations have been issued to allow more flexible use of animal drugs under FDA oversight, aimed at treating and preventing NWS infestations in livestock.7

Import restrictions, surveillance efforts, use of detection dogs, and other agricultural safeguards are being tightened at the border to limit reintroduction via livestock trade.8

Looking Ahead

Although the NWS had been eradicated in the U.S. by the late 1970s, its resurgence in nearby countries signals a looming threat to American livestock and forestry industries. This human case serves as a stark reminder of how travel-linked parasitic threats can reemerge and why robust surveillance, rapid response, and public awareness remain essential.9

While rare, this travel-associated case of NWS underscores the importance of medical vigilance, especially for individuals returning from endemic regions. The swift response by health and agriculture authorities offers reassurance that preventive infrastructure is being strengthened to safeguard both public health and livestock industries.

SOURCES

· 1 People.com

· 2 CDC

· 3 People.com

· 4 The Economic Times

· 5 People.com

· 6 KCRA

· 7 KCRA

· 8 KCRA

· 9 KCRA

This story was created with the aid of ChatGPT.

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