A sharp rise in infections stemming from a parasitic worm that invades the human brain has health officials in the Hawaiian island of Maui worried.

Six cases of rat lungworm disease have so far been confirmed in Maui in the last three months, with more episodes currently being investigated. Given the island had only experienced two documented cases of rat lungworm in the decade before this outbreak, the sudden increase is causing concern.

Rat lungworm disease is caused by the parasitic roundworm Angiostrongylus cantonensis, with the adult form of the parasite found only in rats.

The infection is spread when rats carrying the parasite excrete the larvae of the roundworm in their faeces. From there, it can be picked up by other animals, such as snails, slugs, freshwater shrimp, crabs, and frogs.

If people handle or consume any of these infected animals – or come into contact with them on contaminated food sources, such as raw fruit and vegetables – they too can become infected.

For many, there are no symptoms, and most people recover from the infection on their own. But in some cases, the worm moves into the brain and nervous system, resulting in a parasitic form of meningitis that can cause intense headaches, tremors, numbness, and fever symptoms – and which can ultimately turn out to be fatal.

"The parasites are in the lining of my brain, moving around," Maui resident and preschool worker Tricia Mynar, who believes she contracted the infection while on the Big Island, told Honolulu Civil Beat.

Mynar first experienced symptoms in late February while on a work assignment. She now uses a walker to get around, but struggles with it due to the severity of her tremors.

According to her, the degree of pain inflicted by the parasite varies from day to day and affects different body parts in different ways – but when it's extreme and focused, it can be almost unbearable.

"It was like someone suddenly took a lei needle and pushed it through the soft spot on top of my head, then pushed it down below my left ear, then up to my left temple, then moved from back to front behind my right eye. As the lei needle pain shot out through my right eye there were flashing white lights," the mother of three says.

"Don't ever say to me that labour is hard. Labour is like eating ice cream after surviving the feeling of a lei needle shooting through your brain and out your eye."

According to officials, the parasite has been identified in slugs and snails on Maui, Oahu, Kauai, and the Big Island, and health representatives are urging people to make sure they adequately wash their food to minimise the risk of infection, as well as not touch any slugs or snails.

"I hope people really understand it's in their hands to prevent infection by properly washing all of the produce… regardless where they buy it from," executive director of Hana Heath, Cheryl Vasconcellos, told the crowd at a community meeting in Hana, Maui, last week.

"Everyone needs to be vigilant about it and take precautionary measures."

The Hawaiian Islands on the whole usually average about 10 cases of rat lungworm per year, according to state epidemiologist Sarah Park, who says the symptoms are as random as they are terrifying.

"If you could imagine, it's like having a slow-moving bullet go through your brain and there's no rhyme or reason why it's going to hang out in this part of the brain or that part of the brain," she told Associated Press.

As for what's caused such a spike in Maui recently, nobody's entirely sure, but there are concerns the parasite is being spread by a rise in numbers of an invasive semi-slug in the region, with as much as 80 percent of the species carrying the roundworm.

Behind that, it's possible that increasing globalisation and shipping is to blame for the distribution of the parasite, which was first identified in Taiwan in 1944, but which has spread far and wide in the last few decades.

"[I]t's a worm infection introduced into North America through globalisation," virologist Peter Hotez from Baylor College of Medicine in Houston told Adrienne LaFrance at The Atlantic.

"Some suggest that it's due to snails or slugs in the ship ballasts – ships coming from Asia and going through the Panama Canal."

But climate change could also be playing a role in helping the parasite survive in new ecosystems.

A 2015 study identified the presence of rat lungworm in Oklahoma,"an area predicted to lack suitable habitat for the parasite" – with the researchers commenting that human-caused factors such as global travel, human encroachment into wildlife habitat, and climate change could all influence the distribution and emergence of disease.

As for whether that's what happening here, scientists don't know for sure yet, but the sooner we can put an end to the spread of this life-destroying infection, the better.