The U.S. Department of Health and Human Services on Sunday reported a human New World screwworm (NWS) case.
The case, investigated by the Maryland Department of Health and the U.S. Centers for Disease Control and Prevention, was confirmed by the U.S. Centers for Disease Control and Prevention (CDC) on Aug. 4, and involved a patient who returned from travel to El Salvador, HHS spokesman Andrew G. Nixon said in an email to Reuters.
Gabriel Alvarado, CDC spokesperson, confirms the email saying, “CDC, in coordination with the Maryland Department of Health, 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 CDC through telediagnosis (i.e., expert review of submitted larvae images) on Aug. 4, 2025.”
In response to the confirmation, USDA shared a statement: “In support of CDC’s activities and out of an abundance of caution, USDA initiated targeted surveillance for NWS within a 20-mile radius of the affected area, encompassing portions of the District of Columbia, Maryland, and Virginia. To date, all trap results have been negative for NWS. There have been no detections of NWS in the U.S. in livestock or other animals since the last outbreak of NWS in the Florida Keys was resolved in 2017.”
Reuters reported on Sunday evening that a person who had traveled to the U.S. from Guatemala was confirmed as receiving treatment in Maryland for NWS.
“The risk to public health in the United States from this introduction is very low,” Nixon said.
State veterinarians learned of the human case during a call last week with the CDC.
The exact dates of travel and arrival in U.S. are not confirmed at this time.
South Dakota State Veterinarian Beth Thompson, who was quoted in the story, says when CDC officials confirmed it was NWS, CDC worked with local physicians and dealt with the larva. She says there has been no livestock movement control put into place because of the case.
Thompson says NWS is endemic in some Central American countries.
This is not the first case of a U.S. traveler being infect with NWS. According to a CDC Resurgence of NWS Update webinar:
- In 2014, a woman in her mid-20s returned from a beachside resort in the Dominican Republic where she fell asleep on the beach one night. Pain started in her ear the next day and it was discovered she had NWS when she got back to the U.S.
- In 2023, a mid-60s male traveled to Argentina and Brazil with a fresh surgical wound on his cheek. NWS entered through his wound and he received treatment for larvae infestation once he returned to the U.S.
- In 2024, an individual spent approximately seven days in the Dominican Republic. This individual was immunosuppressed due to a previous case of cancer in their nose. Once the individual arrived back in the U.S., 100 to 150 larvae were surgically removed from their nose.
Two other cases include a 15-year-old girl when she returned from a three-week hiking trip to Peru and a 12-year-old girl who had been on a church mission to Palmira, Colombia.
USDA also confirmed it was not the first case saying, “There have been previous instances of traveler-associated cases of NWS in the United States in years past. In all cases, these instances were isolated and designated as closed after precautionary targeted surveillance in the vicinity was negative. We may continue to see traveler-associated cases of NWS and USDA, in coordination with HHS and CDC, will conduct targeted surveillance to ensure there is no active spread of NWS in the United States. This is not cause for alarm as human risk is low and we have seen several isolated cases in recent years that have not resulted in livestock transmission.”
National Cattlemen’s Beef Association CEO Colin Woodall, says, “NCBA is aware of a New World screwworm case detected in a person traveling from abroad into Maryland. The case was quickly identified and handled by the CDC in accordance with their protocols. Based on what has been shared with state animal health officials, we do not see any elevated risk to the livestock industry at this time. We appreciate the diligence of human health authorities. This case was quickly addressed thanks to existing protocols, and we are thankful for the ongoing coordination between the CDC, state departments of health, state animal health officials, and USDA.”
As more details are available, we will update this story.
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