A flesh-eating parasitic fly that the United States eliminated decades ago is back.

On June 3, 2026, the U.S. Department of Agriculture (USDA) confirmed the first domestic case of New World screwworm (NWS) in decades. As of June 27, there are more than 20 confirmed animal cases in Texas and New Mexico.

The current outbreak began in Mexico and Central America, where more than 185,000 animal cases and over 2,000 human cases have been reported in recent years. As of early June 2026, 10 people had reportedly died.

This sounds like the plot of a zombie-horror summer blockbuster, but it’s not. At least, not for humans.

What Even Is a Screwworm?

Despite the name, the screwworm isn’t a worm, but the larva of the fly Cochliomyia hominivorax. The female flies lay their eggs in open wounds, where the larvae hatch and feed on living tissue.

Human infestations are uncommon because people usually notice an infected wound and seek medical care. In animals, especially livestock, infestations can be much harder to spot. Left untreated, screwworm larvae can kill an animal within a week or two.

Adult flies can move across farms or pastures, laying eggs in new animals. They can also hitch a ride when infested animals are transported, allowing the outbreak to spread to new locations.

Screwworms haven’t been much of a concern because the U.S. eliminated them using a clever strategy: Scientists released sterile male flies into the wild. When they mated with females, no offspring were produced, and the population eventually collapsed. Officials hope the same technique will once again bring the current outbreak under control and prevent future outbreaks.

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How Do Humans Get Screwworm Infestations?

Humans can get screwworms, but it’s rare. The flies typically target open wounds, though they can also lay eggs in exposed mucous membranes, such as inside the nose.

The CDC says that the people most vulnerable to screwworms include:

• People who work around the animals that tend to get infested
• People traveling to places where screwworm flies are common
• People who sleep outside
• People with untreated open wounds

How Is It Treated in Humans?

If people do get screwworms, treatment isn’t as simple as taking medication.

While drugs like ivermectin can be used in animals, they haven’t been studied in controlled trials for humans. Instead, healthcare providers must physically remove every larva from the wound before it can heal properly.

In the current outbreak in the U.S., the only human case reported was in a traveler who returned from El Salvador in August 2025. Human infections are typically linked to travel in countries where screwworm remains established. So far in this outbreak, there have been no reports of anyone getting infected within the U.S.

Is Food Safe During the Screwworm Outbreak?

If you’re wondering whether beef or dairy products from screwworm-infested cattle are unsafe to eat, the answer is no.

The USDA inspection process is designed to identify infested animals and keep them out of the food supply. However, if the outbreak continues to grow, it could have economic consequences. More infestations mean more animals that need treatment or must be removed from production, increasing costs for farmers and disrupting operations. Those costs could eventually be passed along to suppliers, grocery stores, and consumers.

For most people, screwworms aren’t something to lose sleep over. You’re unlikely to get infested, and you don’t need to worry about the safety of beef or dairy products. But if the outbreak worsens, you may notice something else that’s unsettling: higher beef prices.