Data from the Mexican government shows that between the four weeks and mid-August, the number of animals in the New World Screwworm (NWS) that were carnivorous parasites increased by 53%.

While fly larvae infestation mainly affects cattle, Mexican officials also registered cases of dogs, horses, sheep and humans.

Dozens of people have been treated in hospitals in the states of Campchez and Chiapas in southern Mexico, according to local media reports.

In U.S. health authorities said they have confirmed the first human case in a patient returning to the U.S. from El Salvador, which is the increase in affected animals in Mexico.

After releasing sterile male flies to disrupt the insect’s reproductive cycle, the NWS was announced in the United States in 1966 and followed Mexico in 1991.

However, it remains common in tropical and subtropical areas of Central and South America, and has recently spread to the north, the first new case reported in Mexico in November 2024.

Female New World Screwworm (Cochliomyia hominivorax) places eggs on the skin of warm-water animals or in near-open wounds. They are also attracted by mucous membranes such as the mucous membranes of the nose, mouth, eyelids, ears and genitals.

The eggs hatch into blocks, drill into wounds or membranes, and feed on live meat.

Infection, known as myopathy, can cause serious damage if left untreated – and may even prove fatal – the larvae tear the tissue with a sharp mouth hook.

Health officials warn that while fatal cases in humans are rare, older people should be extra careful when suffering from health problems.

Mexico’s Ministry of Health said an 86-year-old woman died in Canche state in July due to skin cancer, exacerbated by invasion of screwworm larvae.

The most risky people are people who work with livestock or those who live in rural areas where livestock appear.

The Centers for Disease Control and Prevention urges possible visits to areas where screwworm flies are flies to cope with symptoms. These include unexplained skin lesions, sensation of larvae moving in the wound or nose, mouth or eyes, and seeing goworms in open soreness.

Experts point out that prevention is key when visiting rural areas in affected areas, which includes keeping any open wounds clean and covered and using repellents.

They also ask people to suspect that they may have been haunted by people seeking medical help.