U.S. Detects First Human Case of Screwworm
Screwworm in humans detected for the first time in the U.S., in a Maryland patient who had recently traveled to El Salvador.
Posted on 26/08/2025 at 17:30
- First human case of screwworm in the US
- CDC confirms diagnosis in Maryland
- Parasite threatens livestock
According to EFE, US health authorities have confirmed the country’s first human case of New World screwworm (Cochliomyia hominivorax).
The infection was detected in a Maryland resident who had recently returned from a trip to El Salvador.
The case was reported by the Centers for Disease Control and Prevention (CDC) and the Maryland Department of Health.
The diagnosis was made on August 4 through telehealth, although it had not been made public until now.
First Human Case of Screwworm, a Parasite That Invades Wounds
🔴 CONFIRMED: FIRST HUMAN CASE OF SCREWWORM IN THE U.S.
The United States confirmed its first human case in several decades of infestation by the “New World screwworm.”
The patient, a resident of Maryland, was diagnosed after returning from a trip to… pic.twitter.com/vtRRCYAAsr— BI NOTICIAS (@BI_Noticias) August 25, 2025
The patient has already received medical attention and is recovering well, according to the CDC.
The screwworm is the larval stage of a fly that infests open wounds in warm-blooded animals.
The parasite burrows into living tissue, advancing like a screw through flesh.
If left untreated, the infestation can cause severe damage and even death, both in animals and in humans.
Rare Cases of Screwworm in Humans
#UnitedStates has confirmed its first human case of infestation by the “New World screwworm” in several decades. @ElOpinadorTV #ImagenDigital pic.twitter.com/XVZpgenehf
— Excélsior (@Excelsior) August 25, 2025
Until now, the screwworm had primarily affected livestock in Central American countries.
Screwworm infestations in humans are considered extremely rare by health authorities.
Medical treatment typically consists of manually removing the larvae and then disinfecting the wounds.
In this case, doctors confirmed that the procedure was successful and the patient is not at risk.
A threat advancing north
The diagnosis comes at a time of heightened concern for the US livestock sector.
The parasite was eradicated in 1966 thanks to a massive sterile-fly release program.
However, recent reports show that the screwworm is moving northward from Central America.
Currently, its presence has been recorded in Costa Rica, Nicaragua, Honduras, Guatemala, Belize, El Salvador, and Mexico.
Economic risk of an infestation of screwworm in humans
The US Department of Agriculture (USDA) published a report on August 20 warning of the potential impact.
According to its estimates, an outbreak in Texas affecting 7.2 million cattle could cause losses exceeding $730 million for producers.
The total economic impact, including ripple effects across the production chain, could reach $1.8 billion.
Texas is the country’s largest cattle-producing state and a highly vulnerable hotspot in the event of an infestation of screwworm in humans.
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