At least 43 people in Canada’s New Brunswick province have contracted a new unknown brain disease that causes muscle spasms, loss of memory, and hallucinations.

According to public health officials, five people have died from the disease since the first reported case in 2015.

“We have not seen over the last 20-plus years a cluster of diagnosis-resistant neurological disease like this one,” said Michael Coulthart, head of Canada’s CJD surveillance network.

The disease caught attention earlier this month when Radio-Canada and CBC obtained a leaked memo that was sent from the province’s public health agency to local physicians.

The memo advised doctors to be on the lookout for patients that have symptoms of the rare brain disorder Creutzfeldt-Jakob disease, but test negative for.

Patients will first came in experiencing spasms. Symptoms will then develop into drooling and even tooth-shattering.

Dr. Alier Marrero, a neurologist leading New Brunswick’s investigation, said patients first came in with pains, spasms, and changes in behavior. But because those symptoms can be linked to many different health conditions, they were not a major concern.

The symptoms then progressed to impaired cognitive abilities, muscle wasting, drooling, and tooth-shattering over the next 18 to 36 months. Some of those patients also experienced extremely disturbing hallucinations, like insects crawling on their skin. 

Marrero conducted a series of tests — brain imaging, spinal taps, and toxicology tests — to ensure the brain disease wasn’t a known neurodegenerative disorder. 

Researchers are left with no answers.

Health experts are working with different national groups to determine what exactly this rare condition is and what exactly causes it.

Valerie Sim, a researcher of neurodegenerative diseases at the University of Alberta, said that it is pretty unusual for a brain disease to have such a wide range of common symptoms.

“There just isn’t enough information yet,” Sim said.