TL;DR
Physicians in New Brunswick reported a growing cluster of patients with rapid, unusual neurological decline beginning in 2019. A subsequent paper concluded there was no new disease, but hundreds of patients and some clinicians dispute that finding and suspect an environmental cause.
What happened
In 2019 two confirmed cases of Creutzfeldt-Jakob disease (CJD) in New Brunswick prompted a specialist response. A local neurologist, Dr Alier Marrero, reported a larger set of patients with rapidly progressive, CJD-like symptoms that repeatedly tested negative for prion disease and other established causes. Over five years the group identified roughly 500 people as part of a so-called cluster, with symptoms ranging from dementia, movement disorders and sensory pain to hallucinations, severe weight loss and delusions. A high-profile research paper published last year reviewed cases and concluded the patients likely had previously known neurological, medical or psychiatric conditions rather than a single novel syndrome. That view is contested by many patients and advocates who believe environmental poisoning is responsible. The BBC reviewed documents and interviewed clinicians, patients and officials; it reports at least one cluster patient chose medical assistance in dying and others are considering it.
Why it matters
- Patient welfare: dozens of people have experienced severe, progressive neurological decline and at least one has pursued assisted dying.
- Public-health implications: initial concern about a contagious prion disease prompted urgent surveillance and a multi-disciplinary response.
- Trust in institutions: disagreement between clinicians, researchers and patients has strained confidence in scientific and governmental handling.
- Diagnostic and research priorities: the dispute highlights challenges in distinguishing new diseases from atypical presentations of known conditions.
Key facts
- Initial trigger: two confirmed CJD cases in New Brunswick in early 2019 prompted investigation.
- Primary clinician: Dr Alier Marrero reported an expanding set of CJD-like cases that tested negative for prion disease.
- Scale: Marrero and colleagues documented about 500 people linked to the cluster over five years.
- Symptoms reported: a wide, heterogeneous range including dementia, tremor, spasms, hallucinations, Capgras delusion, weight loss, pain and hair/skin changes.
- Research conclusion: a paper published last year found the cluster patients likely had previously known neurological, medical or psychiatric diagnoses and did not represent a new disease.
- Internal disagreement: neuropathologist Gerard Jansen examined tissue and reported evidence of Alzheimer’s and Lewy body pathology in some samples.
- Official response: a working group involving federal scientists and neurologists formed; the Canadian Institutes of Health Research offered C$5 million to support investigation.
- Public moment: a March 2021 memo from New Brunswick’s chief medical officer leaked to the press, bringing the cluster to national attention.
- Geography: early cases were concentrated around Moncton and the Acadian Peninsula.
- Patient response: many patients and advocates reject the published conclusion and suspect environmental contamination or a cover-up.
What to watch next
- Whether additional peer-reviewed studies or re-analyses of cases appear — not confirmed in the source.
- Any official government inquiry, regulatory action, or public-health follow-up regarding environmental exposures — not confirmed in the source.
- Legal or compensation claims by patients or families related to the cluster — not confirmed in the source.
Quick glossary
- Creutzfeldt-Jakob disease (CJD): A rare, fatal neurodegenerative disorder caused by misfolded prion proteins; some forms can be transmissible under specific conditions.
- Cluster: A grouping of similar health events or cases in a particular place and time that prompts epidemiological investigation.
- Neuropathologist: A physician-scientist who diagnoses disease of the nervous system by examining tissue, often from biopsies or autopsies.
- Medical assistance in dying (MAID): A legal medical procedure in which a qualified practitioner provides or administers medication that intentionally ends a person’s life, subject to national or regional laws.
Reader FAQ
Is there an established new neurological disease in New Brunswick?
A 2025 research paper concluded the cases represented known neurological, medical or psychiatric conditions rather than a single new disease.
How many people were included in the reported cluster?
Doctors following the cases documented roughly 500 people over about five years.
Have investigators identified an environmental toxin as the cause?
Not confirmed in the source.
Did any patients choose medical assistance in dying?
The BBC reports at least one cluster patient opted for medical assistance in dying and others are considering it.
'The answer cannot be nothing': The battle over Canada's mystery brain disease 8 hours ago Share Save Joel Gunter,senior international reporter, New BrunswickandNadine Yousif,senior Canada reporter, New Brunswick BBC Five…
Sources
- A battle over Canada’s mystery brain disease
- A battle over Canada's mystery brain disease
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