The United States has reported its first human case of New World screwworm, a flesh-eating parasite, in a traveller returning from Central America. The US Department of Health and Human Services (HHS) confirmed the case on Sunday, stating the patient had returned from El Salvador, though beef industry sources said the individual had travelled from Guatemala.
The case, investigated by the Maryland Department of Health and the US Centers for Disease Control and Prevention (CDC), was confirmed on 4 August. An HHS spokesperson said the risk to public health in the US from this introduction is very low. No animal cases have been confirmed this year.
The confirmation comes as the cattle industry remains on high alert, with screwworm moving northwards from Central America and southern Mexico. The US Department of Agriculture (USDA) recently announced plans to build a sterile fly facility in Texas to combat the pest, estimating an outbreak could cost the state's economy around $1.8bn.
New World screwworm is a parasitic fly whose females lay eggs in wounds on warm-blooded animals. The hatched larvae burrow into living flesh, potentially killing the host if left untreated. Human infestations are rare but can be fatal. Treatment involves removing hundreds of larvae and disinfecting wounds, and is typically survivable if caught early.
The patient was treated and prevention measures implemented in Maryland. The CDC notified state health officials and the state veterinarian, though some state officials expressed frustration over the timeliness of information sharing.
