An outbreak of a rare and dangerous parasitic larva known as the New World Screwworm (NWS) has been reported in the United States, with two confirmed human cases in the state of Maryland, according to the U.S. Department of Health and Human Services.
In a statement to Reuters, department spokesperson Andrew J. Nixon confirmed that one of the infected individuals was identified on August 4. A preliminary investigation by the Maryland Department of Health revealed that the patient had recently traveled to El Salvador, where it is believed the infection occurred.
Although the identity and personal details of the infected individuals remain undisclosed, the Centers for Disease Control and Prevention (CDC) has confirmed a second NWS case in Maryland just weeks earlier. That patient had recently returned from a trip to Guatemala, suggesting a travel-related pattern of infection linked to Central America.
Despite these developments, Nixon stated that NWS “does not pose a threat” to the United States, emphasizing that “the risk to public health is very low.”
However, this assessment has been met with skepticism by many American biologists, livestock farmers, and professionals in the meat industry. They claim the parasite may have entered the country as early as two years ago and allege that over two dozen people—primarily livestock workers—have already been infected, particularly in Texas.
The New World Screwworm is the larval stage of a screwworm fly species. Female flies lay eggs in open wounds or sores on warm-blooded animals. When the eggs hatch, the emerging larvae—equipped with razor-sharp mouthparts—begin feeding on the host’s living flesh. If left untreated, the infestation can lead to excruciating pain and eventual death.
While similar to maggots, which typically feed on dead tissue and remain on the skin’s surface, NWS larvae burrow deep into flesh. This unique behavior has earned them the nickname “woodworms of flesh.”
Though human infections remain rare, NWS poses a significant threat to livestock and wild animals. Sources in the U.S. cattle industry say the first American outbreak in animals was detected in Texas, near the U.S.-Mexico border. Several animals have since tested positive for the parasite.
In 2023 alone, at least 24 human cases linked to this parasite were recorded in Texas, according to multiple sources in the state’s cattle and meat production sectors. A CDC official, speaking anonymously, confirmed the accuracy of these reports.
The U.S. Department of Agriculture (USDA) reports that the screwworm fly species responsible is native to countries such as Cuba, Haiti, El Salvador, and the Dominican Republic, as well as other parts of Central and South America. It is, however, considered a new and invasive species in the United States.
The USDA has issued warnings that, if not swiftly controlled, the parasite could completely devastate Texas’s livestock industry, which is valued at approximately $1.8 billion.
In response to the growing threat, U.S. Agriculture Secretary Brooke Rollins visited Texas last week and pledged full federal support.
She announced that the government would take “all necessary measures” to eliminate the screwworm fly species from the country.
