First U.S. Human Screwworm Infection Confirmed in Traveler Returning from El Salvador

Horrifying Screwworm Infection Confirmed in U.S. Traveler After Overseas Trip

The United States has just confirmed its first human case of New World screwworm infection tied to international travel, marking a rare but alarming public health event. The infected individual, a Maryland resident, contracted the parasite after returning from El Salvador, a country currently experiencing an outbreak[1][2][3]. The case was confirmed by the Centers for Disease Control and Prevention (CDC) on August 4, 2025, following an investigation in cooperation with Maryland’s health department[1].

What Is Screwworm Myiasis?

Screwworm myiasis is a parasitic infestation caused by the larvae of the New World screwworm fly (Cochliomyia hominivorax). Unlike most maggots that feed on dead tissue, these larvae are notorious for burrowing into the living flesh of warm-blooded animals—including, in rare instances, humans[1][2]. The maggots feed voraciously on healthy tissue, causing severe pain, inflammation, and, if untreated, potentially fatal damage.

The New World screwworm is typically found in South America and the Caribbean[2]. Its lifecycle begins when adult flies lay eggs in open wounds or mucous membranes. Within hours, the eggs hatch, and the larvae begin to consume living tissue, deepening the wound and expanding the infection.

How the Infection Was Detected

This newly confirmed case is the first travel-associated human infection from an outbreak-affected country to be identified in the U.S.[1][3]. The patient had recently visited El Salvador, where screwworm outbreaks have been reported. Upon returning, symptoms developed that prompted medical evaluation, leading to the discovery of the maggots and subsequent laboratory confirmation by the CDC[1][2].

U.S. health authorities, including the Department of Health and Human Services (HHS) and the CDC, responded rapidly to ensure the patient received appropriate care and to assess potential risks to the broader public[1][2].

Symptoms and Dangers

The symptoms of screwworm infection can be horrifying:

• Severe pain at the wound site
• Swelling, redness, and foul-smelling discharge
• Visible movement of maggots within the tissue
• Fever and systemic illness if the infestation spreads

If not treated promptly, the larvae can cause extensive tissue destruction, secondary bacterial infection, and even death[1][2]. In animals, screwworm infestations have led to significant livestock losses, costing millions in damages.

Public Health Response and Risk Assessment

Despite the alarming nature of the case, U.S. health officials emphasize that the risk to public health remains very low[1][2]. The screwworm fly is not endemic to the U.S., and strict import controls on livestock and pets help prevent its spread. Earlier this year, the U.S. government suspended animal imports at the southern border and announced plans to build an insect dispersal facility in Texas as a proactive measure[1].

The CDC and USDA continue to monitor for potential cases and have protocols in place to detect and respond to any future incidents[1][2].

Historical Context: Screwworm Eradication in the U.S.

The New World screwworm was once a major threat to American agriculture. In the mid-20th century, screwworm infestations devastated livestock across the southern U.S., prompting a massive eradication campaign. By releasing sterilized male flies, the USDA successfully eliminated screwworm from U.S. territory by the early 1980s—a landmark achievement in pest control[1][2].

Since then, only rare, travel-associated cases have been reported, and the parasite remains a major concern in regions of South America and the Caribbean.

Lessons for Travelers

While screwworm infection in humans is exceedingly rare, travelers to outbreak-affected areas should take precautions:

• Avoid contact with open wounds and promptly treat any cuts or abrasions.
• Use insect repellents and protective clothing to minimize fly exposure.
• Seek medical attention promptly if unusual symptoms or wounds develop after travel.

Awareness is especially important for those visiting rural or agricultural regions where screwworm flies may be present.

Looking Ahead

This case serves as a stark reminder of the interconnectedness of global health. Parasitic diseases that may seem distant can reach U.S. shores through international travel[3]. Vigilant surveillance, robust public health infrastructure, and traveler education remain critical to prevent future infections.

As the world becomes more mobile, rare infections like screwworm myiasis remind us that pathogens do not respect borders. Continued cooperation between U.S. agencies and international health authorities will help safeguard Americans from emerging threats.

The Maryland patient is now receiving specialized care, and public health officials continue to investigate the circumstances of the infection. For the general public, the risk remains very low—but the case highlights the need for ongoing vigilance and education about travel-associated diseases[1][2][3].

Original source: Ars Technica – Horrifying screwworm infection confirmed in US traveler after overseas trip