Public health officials investigating a mysterious brain disease in Canada have finally released the findings of a long-awaited study — and not everyone is convinced.
Since 2019, a small town in New Brunswick — a Canadian province bordering Maine — has experienced hundreds of cases of people suffering from hallucinations, spasms, rapid memory loss and the sensation of bugs crawling under the skin.
More than 500 people in the area, mostly in the city of Moncton, were reported to have the disease by local neurologist Dr Alier Marrero, who was the first to raise the alarm.
However, as no definitive diagnosis has ever been made, the area was reported to be suffering from a ‘mystery’ brain disease.
But now, after examining two dozen of those cases, researchers say the odds that a new illness has emerged are less than one in a million — and they believe the patients were instead suffering from known conditions like Alzheimer’s.
Patients and their families are raising concerns over the study, however, after it was revealed scientists on the study had previously received fundingfroma company suspected by some locals to be involved in the outbreak.
Online records reveal scientists on the study worked at a hospital that had received $2million from Irving Oil, which extracts hydrocarbons in the state — with some locals suggesting pollution from these could have been behind the cases.
The scientists who led the study strongly refuted claims that this had any influence over their research, adding that the funding was for a completely separate project.
The above shows a pulp mill in New Brunswick, Canada, where reports suggested mysterious brain diseases had emerged
Locals have raised concerns over the disease saying that it made them sick. Scientists say the mystery disease does not exist, and patients were instead suffering from other conditions
The ‘mystery illness’ theory gained traction in 2021 when Canadian health authorities began investigating cases based on Dr Marrero’s reports.
Patients were recorded in Moncton, home to 79,000 people, and in a sparsely populated area in its north called the Acadian Peninsula.
While more than 500 were reported, researchers found 222 patients.
Known as New Brunswick neurological syndrome of unknown cause, people became concerned in the area that it was being caused by something in the water.
Doctors initially suggested patients had Cruetzfeldt-Jakob Disease, or Prion disease, an extremely rare group of neurologic conditions caused by misfolded proteins in the brain.
But tests for this came back negative.
After a two-year investigation of 25 of the patients, scientists from the University of Toronto and the Horizon Health Network concluded there was ‘no support for an undiagnosed mystery disease in New Brunswick’ and their research ‘revealed well-defined diagnoses.’
Published in the US-based journal JAMA, researchers involved in the study contacted 105 patients in the cluster for evaluation.
Of these, 52 declined further contact while 42 did not respond. In total, 15 patients were evaluated.
Scientists also obtained permission to perform autopsies on the bodies of 11 additional patients in the cluster who had died.
Their causes of death were not revealed.
Evaluations were carried out between November 2023 and March 2025.
Based on autopsies, among patients who had died, seven had a form of dementia.
One had adenocarcinoma — a malignant tumor — one had progressive supranuclear palsy — a rare disease that affects walking, balance and swallowing — and one had vascular dementia.
Another patient had unremarkable autopsy findings, but had previously been diagnosed with a primary psychiatric disorder.
The doctors said all these diseases could have caused the symptoms that were considered to be part of the mystery cluster.
Researchers noted there was an absence of one specific change in the brain across all groups that may suggest common exposure to one factor.
An investigation was launched after Dr Alier Marrero, pictured above, raised concerns over the illness
Among the 14 patients that came forward for neurological tests, 10 agreed to a second evaluation by four movement disorder neurologists and two behavioral neurologists.
Previously, the patients had only been assessed by Dr Marrero.
He had found all 10 patients had myoclonus — a disorder causing sudden and involuntary muscle jerks — while seven had ataxia — a neurological condition caused by a lack of muscle coordination.
But in the new study, only one of the reassessed patients was found to have a cognitive disorder while two were found to have a psychiatric disorder.
Five others were found to have no cognitive deficits, while two were found to be normal.
None were found to have myoclonus or ataxia as Dr Marrero had suggested.
The researchers said they found ‘meaningful discrepancies’ between the documented initial history of the patients’ conditions and their findings on the second assessment.
This included three patients reported to have experienced hallucinations, whose symptoms were not confirmed on second evaluation. And 10 patients initially reported to have a neurological disorder, with this not found on follow-up.
In their conclusion, the researchers said their investigation highlighted the importance of getting a second evaluation for a neurological diagnosis.
They also said their findings highlighted the erosion of public trust in institutions, which has been blamed on Covid vaccine mandates in the pandemic.
Marrero responded to the study, however, telling NBC News: ‘I am in profound disagreement with the study conclusions and have many questions regarding the methods and the content.
‘I am sure that our patients, families, and communities share the same very serious concerns.’
Additionally, the study lists several potential notes under the ‘conflicts of interest’ heading, including that some of the authors had previously worked for Canadian health authorities and a number of pharmaceutical companies – with some saying it calls into question the researchers’ objectivity.
The New Brunswick government’s investigation into the outbreak is ongoing, with the state’s chief medical officer saying this week that it would continue.
Dr Yves Léger said the new study ‘doesn’t change my office’s intention to complete its own investigation into cases of undiagnosed neurological illness in New Brunswick.’
DailyMail.com has reached out to the scientists and Irving Oil but has not received a response.
