Doctors in Canada are somewhat baffled by a mysterious brain disease with no obvious cause.
As far back as 2013, a handful of patients have endured unexplained pain, muscle twitching and even hallucinations, to name a few symptoms.
Medics initially likened the mysterious condition to the deadly brain disorder Creutzfeldt-Jakob disease (CJD), until patient tests came back clear.
In March 2021, Radio-Canada reported medics of New Brunswick province had been warned of a cluster of patients showing signs of a disorder "not seen before".
The province is aware of 48 cases, evenly made up of men and women, aged 18 to 85. Six people are thought to have died with the disease.
Doctors believe the condition is "acquired", not genetic. With no treatment, medics are focusing on relieving a patient's discomfort ahead of further research.
While these 48 cases may be the tip of the iceberg, one medic has urged people stay calm, warning "fear paralyses".
One who knows the impact of this mysterious disease all too well is Roger Ellis, who collapsed on his 40th wedding anniversary two years ago following a seizure.
Healthy until that day, Ellis – who is in his early sixties – has since endured delusions and hallucinations.
Ellis – who also became unusually aggressive – was thought to be dying, however, doctors could not explain why.
Medics initially thought he may have CJD, the most famous form of which is known as mad cow disease.
Tests for CJD, along with other potential causes, have all come back clear, leaving doctors stumped.
Ellis' son Steve was listening to Radio-Canada when he heard about the public health memo.
The retired industrial mechanic is now living in a specialised care home, with his condition stable.
Ellis is one of several patients under the care of Dr Alier Marrero at Dr Georges-L-Dumont University Hospital Centre, in the city of Moncton.
Dr Marrero claims medics first heard about the mysterious disease in 2015, however, one patient is thought to have developed symptoms in 2013. At the time, doctors believed it was a one-off highly-unusual case.
The majority of the 48 patients are thought to have become unwell from 2018 onwards.
They live in New Brunswick's largest city Moncton and its Acadian peninsula, which is made up of fishing communities.
The symptoms are said to be wide-ranging and vary from patient to patient.
In the early days of the illness, an individual's behaviour may change, with them becoming anxious, depressed and irritable. This may be accompanied by unexplained pain, aches and spasms.
Severe insomnia or excessive daytime sleepiness may also occur. A patient could then endure memory problems and speech defects, like stuttering or repeating words, that make it difficult to hold a conversation.
Rapid weight loss, muscle wasting, visual disturbances and co-ordination problems have also been reported.
Some patients require walking aids and wheelchairs due to severe muscle twitching.
Hallucinations have also occurred, as has temporary "Capgras delusion", when a person believes a loved one has been replaced by an imposter.
"It's quite disturbing because, for instance, a patient would tell his wife: 'Sorry ma'am you cannot get in bed, I'm a married man' and even if the wife gives her name, he'd say: 'You're not the real one,'" Dr Marrero told the BBC.
Watch: Prion disease treatment may have been discovered
Suspected patients are being tested for genetic diseases, as well as prions. These are a type of protein that can cause healthy proteins in a patient's brain to fold abnormally, triggering diseases like CJD.
Medics also assess whether the individual may have an autoimmune disease, cancer, an infection, heavy metals in their system or abnormal antibodies – the proteins that help fight off an infection.
As part of an investigation into the disease – led by Dr Marrero – patients are asked about their lifestyle and travel history, as well as medics uncovering any potential environmental factors or dietary sources.
"Our first common idea is there's a toxic element acquired in the environment of this patient that triggers the degenerative changes," said Dr Marrero.
One theory is chronic exposure to a so-called excitotoxin like domoic acid, which was linked to an outbreak of food poisoning from contaminated mussels in the nearby province of Prince Edward Island in 1987.
During the outbreak, a third of those affected endured memory loss, dizziness and confusion. Some fell into a coma and four died.
Researchers are also looking into the toxin beta-methylamino-L-alanine (BMAA). Produced by blue-green algae, BMAA has been linked to Alzheimer's and Parkinson's.
While it may sound alarming, cases have not been reported outside of the Acadian peninsula and Moncton.
Dr Marrero has stressed: "Work with hope not with fear, fear paralyses".
Watch: What is mad cow disease?