U.S. Confirms Rare Screwworm Infection: A Cautionary Tale for Public Health

Philadelphia, August 26, 2025 – On Monday, August 25, the U.S. Department of Health and Human Services confirmed the nation’s first travel-associated human case of New World screwworm—a flesh-eating parasitic fly infection—since the mid-20th century. The patient, who recently returned from El Salvador, was diagnosed on August 4, and has now fully recovered, per Maryland health officials and the CDC.ReutersAP News

Understanding the Threat: What Is the Screwworm?

The New World screwworm, scientifically known as Cochliomyia hominivorax, is a parasitic blowfly whose larvae burrow into living flesh—causing a condition medically termed myiasis. Unlike most maggots that feed on dead tissue, screwworm larvae invade healthy tissue, worsening wounds and drawing more flies.Wikipedia

Historically, the United States successfully eradicated the screwworm via the sterile insect technique—a pioneering pest-control strategy that disrupted the fly’s reproduction by releasing sterile males. Eradication was largely complete by the 1960s, but new cases emerged in southern Mexico by late 2024, prompting serious concern.WikipediaScientific AmericanSuccessful Farming

Breaking Down the Lifecycle (Infographic Above)

The infographic illustrates the screwworm’s cycle:

1. A female lays eggs on open wounds or bodily openings.

2. Larvae hatch and burrow into tissue within days.

3. After feeding for about a week, they drop into the soil to pupate.

4. Adult flies emerge in about a week, mate—with females mating only once—and repeat the cycle.

These biological traits make swift containment efforts critical.Wikipedia

Containment Efforts & Travel Advisories

Officials have moved quickly:

• USDA and CDC are reviving sterile-fly release programs—building on proven past successes.

• A sterile fly production facility is under construction in South Texas, and programs are planned for northern Mexico.The TimesReutersScientific AmericanAgroLatam

• Livestock import halts from Mexico have been enacted to reduce cross-border spread.WikipediaReutersThe Times

• Public risk remains very low, according to CDC and HHS statements, and there is no evidence of human-to-human transmission.AP NewsReutersFox News

Officials are urging travelers—especially those visiting rural regions or animal-focused destinations—to monitor and protect any wounds, seek prompt medical evaluation if necessary, and inform physicians about any travel to areas with active screwworm outbreaks. AP NewsThe Times of India

Why This Matters

• Public Health & Agriculture: Though the immediate health threat is low, the screwworm poses a major danger to livestock and could have severe economic impacts—particularly in states like Texas, which is deeply invested in cattle production.ReutersWikipediaThe Times

• Historical Significance: The return of screwworm to the U.S. brings us face-to-face with a bygone era of agricultural peril, reminding us of both the triumphs of eradication and the fragility of those gains.

• Renewed Vigilance Required: Continued global travel, trade, and climate shifts underscore the importance of surveillance, swift response systems, and sustained funding to prevent resurgence.

Summary Table: Key Details