Potential for travel-associated New World Screwworm Myiasis

Actions requested

Be Aware: An outbreak of New World screwworm (NWS) myiasis is occurring in Central America and Mexico among animals and people, with animal cases recently detected in Mexican state of Tamaulipas, which shares a border with Texas.

• New World screwworm (NWS) is a parasitic fly (Cochliomyia hominivorax) which lays eggs in wounds or other body cavities of warm-blooded animals. These eggs hatch into larvae (maggots) that feed on living tissue.
  • Infestations of NWS maggots can cause painful, foul-smelling wounds. Without early detection and treatment, it can lead to extensive tissue damage, and in severe cases, death.
• In August 2025, there was a confirmed human case of travel-associated NWS myiasis in a patient who returned to the United States (Maryland) after travel to El Salvador.
• There have been no cases of NWS identified in travelers in Washington state associated with this outbreak as of January 23, 2026; however, travel-associated cases are possible due to the ongoing outbreak.

Assess travel history

• Healthcare providers who identify visible larvae or egg masses in a patient should ask about recent travel to a country where NWS is present.
• Advise patients who may be travelling to areas where NWS is present on precautions to take to protect themselves from infestation and to monitor themselves for signs and symptoms of NWS myiasis.
• Advise patients experiencing symptoms after recent travel (within 10 days before symptom onset) to contact a healthcare provider for evaluation.

Management

• If you suspect NWS myiasis, immediately contact Public Health.
  
  • Identification of NWS relies on confirmation by the CDC, so arranging for parasite identification of larvae is critical.
    
• It is critical to handle suspected cases of NWS in accordance with Public Health direction. Failure to remove and properly dispose of ALL larvae or eggs may result in the new introduction and spread of NWS in the local environment.
  
  • All larvae and eggs should be accounted for to ensure proper disposal of parasite material.
    
• Coordinate with Public Health to submit larvae to CDC for confirmation.

Report: Immediately report suspected human cases of New World screwworm myiasis to Public Health at 206-296-4774.