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New Brunswick’s health minister says public-health investigators are increasingly questioning the existence of a new and mysterious brain disease that has sparked fears across the province.

Health Minister Dorothy Shephard told a news conference Wednesday that an epidemiological study into 48 suspected cases of the illness did not find any evidence of a common exposure that could have triggered a potentially new neurological syndrome. Instead, she said, provincial health officials believe many of those cases may have been misclassified by a single neurologist working in the province.

For months, New Brunswickers have been anxious to learn more about a cluster of patients with symptoms similar to those of Creutzfeldt-Jakob disease, including memory loss, balance problems and hallucinations – all supposedly associated with an unknown brain disorder. An investigation into the cluster fuelled fear and speculation that people were becoming ill from eating contaminated wild game or seafood, or were exposed to industrial herbicides or toxins from a former lead smelter in northern New Brunswick.

Investigators have now ruled all of those potential causes out.

“Based on the findings of the report, we have learned that New Brunswickers are not at risk from any behaviours, foods or environmental exposures within the province,” Ms. Shephard said.

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Nine people in the cluster have died since 2019, stoking further fears. But a leading Canadian neuropathologist who examined the patients now says the deaths were actually because of known diseases that were misdiagnosed.

Dr. Gerard Jansen of the University of Ottawa, who studies rare progressive neurodegenerative disorders known as prion diseases, says in a recent report on the deaths that they were “misclassified clinical diagnoses.” He identified health issues among the patients that included Alzheimer’s disease, metastatic cancer, frontotemporal degeneration, Lewy body disease and vascular disease.

The Health Minister said the study into the cluster will be completed in January. She told reporters that it is unlikely there is a mystery disease attacking people in the province.

“While I’m not going to predetermine the outcome of the clinical investigation, I believe we’re getting closer to a determination. I also believe Public Health has significant reason to question the validity of an unknown neurological illness,” Ms. Shephard said.

Of the 48 cases included in the study, 46 of them were referred to the Public Health Agency of Canada by a single neurologist – a Moncton specialist named Dr. Alier Marrero. Health officials noted that no cases with similar symptoms were reported outside his catchment area.

That finding prompted the province to change the rules around how patients identified as “potentially having” an unknown mystery brain disease are reported to the national public health agency. In a memo sent to health care providers across New Brunswick this week, the province says that each new case will require sign-off from two specialists before being reported.

Ms. Shephard said the investigation has also identified “gaps” in the way some suspected diseases are identified. She suggested the 48 cases were flagged to the national public health agency before a thorough study could be done to determine whether there was indeed a cluster, and before the province was notified.

The Health Minister also addressed the families of those who have become ill. She told them she hopes they get answers soon. An oversight committee with six neurologists is working to determine whether there are alternate diagnoses for the patients included in the cluster, or whether more investigation is required.

“We know this has been difficult, and you deserve answers,” she said. “If we find at the end of this there is indeed a cluster of unknown neurological cases, we will go further.”

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