The Mexican government recently published a report for Epidemiological Week 39 that included data on the northern spread of the New World Screwworm (NWS).
Historically found in South America, Cuba, Haiti, and the Dominican Republic, parasitic flies carrying the NMW virus, which usually infect cattle, have infected 55 people in Mexico in 2025.
Mexico stated on October 6, 2025, that infestations can be severe and lead to sepsis if untreated, but are not contagious. Flies carrying NWS lay eggs in animal and human wounds, causing larvae to feed on living flesh.
These infestations have been found close the the Mexico-United States border, in Nuevo Leon.
The U.S. CDC says once detected, healthcare providers should remove the NWS larvae from the affected site immediately.
Seperately, Reuters reported the NWS outbreak has rattled the livestock sector in Mexico and the United States since May 2025.
Mexico's agriculture ministry and sanitation agency, Senasica, recently confirmed that ivermectin must be administered 72 hours before the cattle movement, under the supervision of staff from the International Regional Organization for Animal and Plant Health.
Last summer, the U.S. Department of Agriculture implemented extensive plans to prevent the northern spread of NWS.
In October 2025, the U.S. Food and Drug Administration conditionally approved Dectomax-CA1 (doramectin injection) injectable solution for the prevention and treatment of NWS larval infestations, as well as the prevention of NWS reinfestation for 21 days.
Dectomax-CA1 is conditionally approved for use in cattle, not for human use.
