US Confirms First Human Screwworm Case Linked to Travel

Diseases carried by insects and parasites aren’t limited by borders. With international travel so common, it’s not unusual for health agencies to report cases of infections that were contracted abroad and later diagnosed in the United States.

Most of these incidents are rare, and while they can sound alarming, they highlight how carefully public health teams monitor potential threats. The latest case making headlines involves the New World screwworm, a parasitic fly whose larvae feed on the living tissue of warm-blooded animals.

On August 4, US health officials confirmed the first human case of travel-associated New World screwworm myiasis. The patient, a Maryland resident, had recently returned from a trip to El Salvador.

Andrew G. Nixon, spokesman for the Department of Health and Human Services (HHS), told Reuters that the Centers for Disease Control and Prevention (CDC) identified the larvae as belonging to the New World screwworm fly. Nixon stressed that the current “risk to public health in the United States is very low,” adding that no animal cases have been detected this year.

The parasite in question is Cochliomyia hominivorax, better known as the New World screwworm fly. Its larvae are notorious for feeding on the flesh of living animals, including cattle, wildlife, and, in rare cases, humans. The US Department of Agriculture (USDA) has called it a “devastating pest” because of the severe damage it can cause to livestock.

Screwworm flies, once eradicated in the US, resurface as a growing threat moving north through Mexico

The fly is native to parts of Central and South America, as well as the Caribbean, with established populations in Cuba, Haiti, and the Dominican Republic. It was once widespread in the US but was eradicated in the 1960s through aggressive control programs.

The USDA has previously warned that screwworms have been detected moving north through Mexico. Adult screwworm flies resemble common houseflies, but their larvae are the real problem.

Measuring between 6.5 and 17 millimeters, the maggots have distinct bands of spines around their body segments. They burrow into open wounds to feed, which is where the name “screwworm” comes from.

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Screwworm flies pose deadly risks by laying eggs in even the smallest wounds of animals and newborns.

Female screwworm flies lay eggs around wounds, no matter how small. The Equine Disease Communication Center (EDCC) notes that even something as minor as a tick bite can be sufficient for egg-laying. These eggs, creamy white in color, hatch within 12 to 24 hours.

The larvae then spend about a week feeding on living tissue. This feeding creates large, foul-smelling wounds that can reach 10–12 centimeters across. In animals, telltale signs include unusual agitation, persistent head shaking, a rotten odor, and, most visibly, maggots in wounds.

For newborn animals, the risks are especially high. Flies will sometimes target the umbilical cords of calves or foals, causing life-threatening infections if not treated quickly.

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If screwworms are suspected, experts advise immediate medical or veterinary attention. The USDA points out that there are currently no FDA-approved animal drugs specifically for New World screwworm infections.

However, veterinarians may rely on alternative treatments that have shown effectiveness in controlling the larvae. For humans, treatment typically involves removing the larvae and cleaning the wound thoroughly. When diagnosed quickly, cases can be managed, but untreated infections can be fatal.

Interestingly, the media plays a significant role in shaping public perceptions and reactions to health-related news. The media's framing of diseases can induce both rational and irrational fears. As noted by Dr. Adam Grant, organizational psychologist, "The way we perceive risks is often influenced more by the stories we hear than by the actual statistics." This highlights that media-induced fear can lead to large-scale behavioral changes, including increased health screenings and altered travel plans, even when the actual risk is low.

First US case of travel-related New World screwworm confirmed in Maryland patient after trip to El Salvador

According to a CDC official:

“In coordination with the Maryland Department of Health, [we] investigated a confirmed case of travel-associated New World screwworm in a patient who returned from travel to El Salvador. The case was confirmed by the CDC through telediagnosis (i.e., expert review of submitted larvae images) on August 4, 2025. This is the first human case of travel-associated New World screwworm myiasis from an outbreak-affected country identified in the United States.”

The CDC advises anyone who suspects they may have contracted the parasite to contact them directly for guidance. They also stress that while the case is unusual and concerning, the broader risk to the US population remains minimal.

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Understanding the Psychology Behind Fear of Diseases

The fear of diseases, particularly those linked to parasites and insects, is deeply ingrained in our psychology. This fear, known as parasitophobia, can be attributed to our hardwired survival instincts. According to a study by Davey (2011), this fear is often amplified by unfamiliarity and perceived uncontrollability associated with such diseases, which could explain the heightened anxiety seen in cases like the New World screwworm.

Human cases of screwworm are rare, but the parasite’s ability to spread rapidly among animals is what makes it a serious concern for agriculture and wildlife management. Even a small outbreak could have devastating effects on livestock, costing millions in economic losses.

This case shows how easily parasites can travel across borders and why monitoring is essential. Travelers returning from regions where the screwworm is still present are urged to be vigilant about unusual wounds and to seek care promptly if they notice anything unusual.

What Research Shows About Health Communication Strategies

Effective health communication strategies are crucial to temper fears and promote informed decision-making. According to Gretchen Rubin, happiness researcher, "When we communicate effectively, we can alleviate anxiety and foster a sense of safety." Furthermore, Dr. Daniel Goleman, emotional intelligence expert, emphasizes that "being aware of our emotions and those of others can empower individuals to make informed decisions rather than succumbing to fear." By implementing these strategies, health communicators can better support the public in navigating health-related concerns.

Analysis & Alternative Approaches

In conclusion, understanding the psychological underpinnings of fear and the influence of media can significantly enhance public health communication. It is important to remember that while fear can be a powerful motivator for change, it can also lead to irrational behaviors if not properly managed. Therefore, ongoing research into effective health communication strategies is essential in our interconnected world where diseases know no borders. (World Health Organization, 2015)