Potential Neurological Syndrome

Investigation of a Cluster of a Potential Neurological Syndrome of Unknown Cause in New Brunswick



Public Health New Brunswick (PHNB) has been investigating a potential neurological syndrome of unknown cause that was suspected of affecting some residents of New Brunswick.

An oversight committee reviewing the case files of all 48 of the potential cases found that the patients didn’t have symptoms in common or have a shared common illness.

A separate in-depth epidemiological investigation last fall concluded the patients didn’t have any common behaviours, foods or environmental exposures.

Following these reports, all the patients were excluded from the cluster and the Minister of Health has accepted the conclusion that no such neurological syndrome of unknown cause exists in New Brunswick.

This webpage is to provide the public with access to all the reports compiled during this process. You will find links to the Epidemiology Report, the Oversight Committee Report as well the conclusions of Public Health New Brunswick.

This webpage is to provide the public with access to all the reports compiled during this process. You will find links to the Epidemiology Report, the Oversight Committee Report as well the conclusions of Public Health New Brunswick.

It’s important to understand that outbreak investigations are not rare. Public Health routinely carries out outbreak investigations of varying types, from enteric diseases, to food-borne illnesses and other bacterial or viral-vector diseases. Every cluster or outbreak with an unknown cause is considered a “mystery illness” until an outbreak investigation can be done to find out why people are becoming ill. When disease outbreaks or other public health threats emerge, Public Health teams investigate, identify the cause, rapidly implement control measures, and collect evidence to recommend preventive actions.

In New Brunswick, experts in a variety of fields constantly test and investigate reports of any credible source that could be a risk to public health. A few areas you may be familiar with include things like testing ticks for Lyme Disease, testing deer and moose for “chronic wasting disease” or monitoring our water sources for blue-green algae blooms.

If anything is found to be a threat, it is published on the New Brunswick Public Health Advisories webpage.




Final Report and Recommendations

New Brunswick healthcare providers play a critical role in the early detection of clusters and outbreaks of disease. Continued support of this collaborative approach between physicians and Public Health New Brunswick (PHNB) is necessary for timely outbreak investigations.

The PHNB investigation of a neurological syndrome of unknown cause, including the Epidemiological Summary of Enhanced Surveillance Interviews and the Oversight Committee Report, concludes there is no evidence of a cluster of a neurological syndrome of unknown cause.

PHNB is therefore concluding its investigation into a neurological syndrome of unknown cause and recommends that patients who were advised they may have a neurological syndrome of unknown cause contact their primary care provider for a referral to seek treatment and care at the Moncton Interdisciplinary Neurodegenerative Diseases (MIND) Clinic or with another specialist physician.

Oversight Committee Report

In the context of a public health investigation led by Public Health New Brunswick (PHNB), the oversight committee, created expressly to provide independent expert oversight and recommendations regarding cases that were identified as part of a cluster with a potential neurological syndrome of unknown cause, presented its findings.

The committee found that out of 48 cases, none fulfilled the full criteria of the case definition. In light of these findings, the committee concluded that although some of the cases have presentations with unusual symptomology, they do not appear to have a common illness with an unknown etiology and there is no evidence of a cluster of neurological syndrome of unknown cause

Epidemiology Report

New Brunswick’s Epidemiology and Surveillance branch released its report on the investigation of the potential neurological syndrome of unknown cause in October 2021. The report was exploratory in nature and did not establish any links between common exposures and the potential neurological syndrome.   The epidemiological report concludes that New Brunswickers should feel confident that they are not putting themselves or their families at risk by consuming regional foods and that there are no specific behaviours or environmental exposures that can be identified as potential risk factors.

Since concerns were raised about exposure to algae blooms, the team took extra care to explore this potential area of exposure. The epidemiological investigation does not point to algae blooms as being a potential source or cause of symptoms.

The epidemiological report is one part of a two-pronged investigation.

Additional Resources

Frequently Asked Questions

Where did this potential Neurological Syndrome of Unknown Cause come from?
An investigation into the possible existence of the Neurological Syndrome of Unknown Cause evolved during ongoing discussions between a Moncton neurologist and the national Creutzfeldt-Jakob Disease Surveillance System (CJDSS).

The CJDSS is a federal body that works with provinces and territories to monitor cases of human prion diseases, like Creutzfeldt-Jakob Disease (CJD).

During routine case monitoring, the CJDSS noticed an unusual number of referrals from New Brunswick of people who had symptoms similar to CJD but tested negative for any known prion disease. The CJDSS and the neurologist categorized them as part of a cluster of a potential neurological syndrome of unknown cause.

In late 2020, the CJDSS notified Public Health New Brunswick of these cases. By the end of April 2021, a total of 48 individuals had been formally identified as part of the cluster. Of those, 46 were referred by one neurologist.

How are “mystery illnesses” investigated?
Every cluster or outbreak with an unknown cause is considered a “mystery illness” until an outbreak investigation can be done to find out why people are becoming ill. When disease outbreaks or other public health threats emerge, Public Health teams investigate, identify the cause, rapidly implement control measures, and collect evidence to recommend preventive actions. The Center for Disease Control refers to these teams as “Disease Dectectives”.

For example, in 1999 there was a cluster of severe cases of encephalitis in New York city. At the same time an unusual number of dead birds were seen in and around the city. Although not seen in North America before, the investigation identified West Nile virus infection as the cause. Depending on the findings during an investigation, investigators may explore different areas. For example, one investigation could include testing food samples for a pathogen like E coli which might trigger food recalls. Another investigation could warrant testing of drinking water and this might result in changes to make sure the water supply system is safe. Other investigations might not include any testing at all.

In this case Public Health New Brunswick met with multiple experts to try to answer basic questions. Who is sick? What are their symptoms? Is there any pattern in symptoms among the sick people? When did they get sick? What is causing them to be sick? Is the sickness related to any exposure to a particular substance or environmental factor? Where could they have been exposed?

An outbreak investigation follows the same methodology as the CDC’s Principles of Epidemiology in Public Health Practice. Please note that several steps may be tackled at the same time, or the circumstances may dictate that a different order should be followed.

During the investigation of a potential Neurological Syndrome of Unknown Cause Public Health opted to conduct both an epidemiological investigation which was completed in October 2021, as well as a clinical investigation which was completed in February 2022.

Were blue-green algae toxins investigated as a possible cause?
All environmental exposures were considered as a possible source including blue-green algae. However, there wasn’t enough evidence to consider any one source over another until a full epidemiological investigation could take place. In the meantime, sample collections for blue-green algae (cyanobacteria) so that testing could take place at a later date if needed. It’s worth noting that the summer of 2021 didn’t have the weather conditions conducive to the production of blue-green algae, so no blooms were detected, and therefore no samples were taken.

Several municipal, provincial and national entities coordinate resources to constantly monitor water quality in our watersheds and the drinking supply of all residents of New Brunswick.

Local governments work and collaborate with both the Department of Health and the Department of Environment and Local Government to ensure we are proactive and adopt a preventative approach to protecting the drinking water supplies and water quality delivered to residents of the province, as well as meet or exceed standards related to recreational municipal bodies of water.

The Department of Environment and Local Government (DELG) and Department of Health (DH) provide surveillance for harmful algae blooms which may be present in freshwater bodies in the province. Fisheries and Oceans Canada (DFO) is responsible for safeguarding Canadian waters and managing Canada's fisheries and oceans resources, including similar surveillance of shellfish in saltwater bodies through the Canadian Shellfish Sanitation Program.

When algal blooms are reported in the province samples are collected and analyzed to determine the type and concentration of algae present, including blue-green algae (cyanobacteria). Blue-green algae advisories are then issued accordingly. During 2021, DELG agreed to collect additional samples from water bodies with blue-green algae blooms for further analysis; however, the conditions that produce algae blooms were not present in that year and no algae blooms were observed during the warmer summer months; additional sampling did not occur.

Public Health maintains a Blue-Green Algae page with all present and past public advisories.

Fisheries and Oceans Canada maintains a real-time Shellfish harvesting map of openings and closures of Canadian harvesting areas for bivalve shellfish (mussels, oysters, clams and scallops).

Patients say the oversight committee didn’t see them or test them. How did they decide on a conclusion or recommendation?
The Oversight Committee’s role was not to diagnose the patients. Instead, it was to review the clinical files of each individual and determine whether they met the case definition.

The clinical information was obtained from several sources including the patients’ primary care physicians and specialists, the Government of New Brunswick electronic health records, and the hospital electronic medical records where patients were assessed, followed, or received treatment as an inpatient or outpatient. This included all the information that could be obtained about the patient’s health history, family health history and symptoms, as well as brain imaging and other laboratory diagnostic tests.

This information, and the oversight committee members’ clinical experience and expertise, was used to help determine whether there are alternate diagnoses for the patients or whether more investigation would be needed.

This is not unique to this situation. It is not uncommon for referrals to be reviewed and potential diagnoses identified without a patient being seen in person.

What happens to the patients now?
Some of these patients have serious known conditions that are impacting their lives in profound ways and several patients need follow-up testing, assessment, and care.

As each case review was completed, the Oversight Committee sent a letter to the patient’s primary care provider with its conclusions and/or recommendations for further clinical review, and then sent a communication to the patient directly.

All of the patients were asked to follow up with their primary care provider and will continue to have access to a specialist at the MIND Clinic in Moncton or any other specialty physician.


What happens to the MIND Clinic now?
The MIND Clinic's mission extends beyond the assessment and care of the patients identified as part of the cluster investigated by New Brunswick Public Health.

The MIND Clinic is New Brunswick’s only cross-specialty collaborative clinic for all neurodegenerative diseases affecting adults of any age. Its mission continues to be the assessment, diagnosis, and ongoing care/treatment to adult patients with progressive neurodegenerative diseases.

All patients referred to the clinic have a combination of signs and symptoms that are progressive and difficult to assess, diagnose and care for by a single physician. The types of diseases (“neurodegenerative diseases”) that are assessed are those that cause changes in the brain and spinal cord that lead to progressive problems with mental functioning and physical movements.

The MIND Clinic will also be conducting important research to improve our understanding of neurodegenerative diseases in New Brunswick and will study how we can identify and treat these conditions so that patients can receive optimum care at all stages of their illness.


Will you be allowing national experts to conduct research?
Public Health NB has worked very closely with a multitude of national experts throughout this investigation. We have posted links on our webpage to ongoing municipal, provincial and federal collaborations to ensure safe drinking water, for the monitoring of environmental toxins and contaminants, and the safe harvesting of fish, lobster and shellfish. Particular attention was paid to cyanobacteria toxins produced by blue-green algae as this is a known risk to public health. No link was found to this cluster as part of this investigation.

The scientific and research community actively investigates a multitude of subjects to further our knowledge and understanding of environmental risks to human health. Public Health New Brunswick remains committed to supporting these efforts in its mandate to protect the health and safety of New Brunswickers.

In addition, the MIND Clinic will collaborate with local, provincial, and national experts on research projects that are applicable to the conditions impacting patients and families associated with the MIND Clinic. All potential research studies will undergo a feasibility assessment by the MIND Clinic, a review by Horizon’s Human Research Protection Program, and then approval will be obtained from Horizon’s Research Ethics Board (REB) and any research partner’s REB.

With research ethics approvals in place, the informed and voluntary consent of potential research participants will be sought from patients at the MIND Clinic.


Privacy Statement

When disclosing information, Public Health New Brunswick (PHNB) always:

  • respects the imperative need to find the right balance between the public’s need and right to know, and the duty to protect the privacy of all New Brunswickers
  • follows the principle of necessity and proportionality: information is disclosed in a manner that does not permit the identification of affected individuals but is sufficient to fully inform the public

The findings presented here follow applicable privacy legislation, including the Personal Health Information Privacy and Access Act (PHIPAA), the Right to Information and Protection of Privacy Act (RTIPPA), as well as best practices to ensure every individual’s right to privacy is protected at all times.

Some of the information used for this investigation was collected directly from individuals, who provided their informed consent, which included assurance that no personal or identifying information would be disclosed in the report of findings.