The US has confirmed its first human case of the New World screwworm, a flesh-eating parasite that originated in South America and has been detected in Mexico. The Centers for Disease Control and Prevention (CDC) announced the case on August 4 in a patient who had returned from travel to El Salvador.
According to experts, the screwworm is typically found in South America and the Caribbean, but infestation occurs when fly larvae feed on tissue or flesh of warm-blooded animals. Infected individuals can experience painful wounds that can lead to sepsis if left untreated.
The US has previously eradicated the screwworm, but it’s spreading again due to factors such as the movement of infested cattle and a possible decrease in effectiveness of sterilized flies. To combat the threat, the US Department of Agriculture (USDA) is building its only sterile-fly production facility at an Air Force base in Texas.
The USDA aims to produce up to 300 million sterile flies weekly to prevent the spread of the screwworm. The agency is also hiring more mounted patrol officers and investing $100 million in technologies to combat the parasite.
Agricultural groups welcomed the announcement, calling it a proactive step to eradicate the parasite from within the US borders.
Source: https://www.npr.org/2025/08/25/nx-s1-5515487/new-world-screwworm-us-human-case