Rat lungworm has long been prevalent in parts of Asia and the Caribbean—the first human case of the disease was recorded in Taiwan in 1944—but only recently has it been identified routinely in the United States, including in Hawaii, California, Alabama, Louisiana, Florida, and elsewhere along the Gulf Coast, according to a 2015 study in the Journal of Parasitology. The geographical distribution of this disease has “changed dramatically” in just a few decades, wrote the authors of a separate study, published in the Hawaii Journal of Public Health in 2013.

“So it’s a worm infection introduced into North America through globalization,” said Peter Hotez, the dean of the National School of Tropical Medicine at Baylor College of Medicine. “Some suggest that it’s due to snails or slugs in the ship ballasts—ships coming from Asia and going through the Panama Canal.”

Transmission to humans often occurs when people eat intermediate hosts—a tiny, translucent slug might be imperceptible on a leaf of lettuce that wasn’t adequately washed, for example. Even the slime left behind by an infected slug carries a transmission risk. (Eating raw or undercooked freshwater prawns, crabs, and frogs is also a risk factor.)

In Hawaii, health officials are warning people not to handle backyard slugs or snails with bare hands. Officials there have been closely tracking the disease for years. But a rash of new cases of the disease has people there rattled. There have been half-a-dozen reported cases of the disease on Maui over a three-month period this spring, three times as many as had been reported in the entire decade up to that point, according to the Maui News.

Rat lungworm disease is notoriously hard to diagnose, largely because there is no blood test that can confirm an infection. (Usually, doctors can determine whether someone is infected based on a patient’s symptoms and exposure history, or a test of cerebrospinal fluid.) There’s no treatment for the disease, though patients are often given painkillers to manage symptoms. Rat lungworm disease can resolve on its own, once the worms die, but in some cases it is fatal.

“I have parasitic meningitis,” said Tricia Mynar, a Maui woman diagnosed with the disease, in an April interview with Honolulu Civil Beat. “The parasites are in the lining of my brain, moving around.”

Mynar described her pain from the disease as worse than childbirth, saying it feels like “somebody opens the top of my head, sets a hot iron inside my brain, then pushes the steam button.”

“Tremors are the hardest part,” she told Honolulu Civil Beat. “They affect me so bad that sometimes I can’t hear my own speech.”

Now, public-health officials elsewhere are anticipating an uptick of cases of the potentially deadly disease across the United States—and trying to figure out just how far it will spread. Global travel, human encroachment into wildlife habitats, and climate change are all factors that will play a role, they say.