What Is New World Screwworm

New World Screwworm First Human Case Reported in the US.

The first human case of New World screwworm infestation has been confirmed in decades in the United States. The patient is a travelling El Salvadorian who was diagnosed in early August 2025. Health officials underline that there is no significant threat to the health of people , but the case is an indicator of the possible reappearance of a species of a parasite that has been eliminated in the area.

What Is New World Screwworm?

The screwworms of Blue-grey blowflies that are native to South America and the Caribbean are new world screwworms. Eggs are laid by female flies on exposed wounds or natural body orifices of warm-blooded animals--and in rare cases of humans. The females reproduce upto 3, 000 eggs in their lifespan of 10-30 days. The eggs are deposited, and once hatched they develop into larvae which burrow into living tissue, which causes them painful wounds.

The screw-like burrowing of the larvae is how the name screwworm was derived. Without treatment, the cases could continue to spread to sensitive parts of the body like the brain, which causes severe infections, sepsis, and even death.

Eradication and Reemergence

In 1966 , the US eradicated screwworms with sterile insect technique (SIT) that involved the release of billions of sterile male flies to interfere with reproduction. The technique also has eliminated infestations in Mexico and much of Central America by the beginning of the 2000s, and had occasional outbreaks since, most recently in Florida in 2017.

Nevertheless, within the recent years, there have been re-emergences of cases in Panama, Costa Rica, Nicaragua and Honduras . Scientists associate the resurgence of the parasite with the transportation of infected animals and potential diminished efficacy of SIT with newer strains.

Public Health Response

According to US officials, the ongoing outbreak is of little risk , but surveillance and early diagnosis is necessary. Wider spread can be mitigated by creating awareness amongst the travellers and healthcare givers. Experts also call for:

• Increasing sterile insect programmes.
• International collaboration to trace movement of livestock.
• Ongoing studies to overcome developing strains of the screwworms.

Outlook

Although the single case in the US is not an indicator that the threat is far-reaching, it is a wakeup call that care should be taken. The key effort to ensure the prevention of the reoccurrence of the parasite across the Americas will be renewed control efforts and cooperation between the countries.