CDPH/Health Advisory– September 4, 2025 – The California Department of Public Health (CDPH) would like to alert healthcare providers, local health departments, laboratories, and travelers about increased detections of New World Screwworm (NWS) in southern Mexico and Central America, where it had been previously eradicated. NWS is a parasitic fly whose larvae feed on living tissue and can infest mammals and birds; it largely affects livestock but can also affect pets, wildlife, and humans. The US Department of Health and Human Services (HHS) and the U.S. Centers for Disease Control and Prevention (CDC) recently announced identification of a travel-associated case of NWS infestation in a U.S. resident who traveled to El Salvador. Healthcare providers who identify myiasis in a patient should ask about recent travel to a country where NWS is present and notify their local health department (LHD). The LHD should notify the California Department of Public Health (CDPH) of any suspected human cases. Suspected cases of NWS infestation in animals must be reported to the California Department of Food and Agriculture (CDFA).
Please see the full US Department of Health and Human Services (HHS) and the U.S. Centers for Disease Control and Prevention (CDC) press release here: https://www.hhs.gov/press-room/hhs-cdc-usda-traveler-associated-screwworm-case-surveillance.html
The full CDPH health advisory here: https://www.cdph.ca.gov/Programs/OPA/Pages/CAHAN/New-World-Screwworm-Outbreak-in-Mexico-and-Central-America.aspx
