Five hundred people in a small Canadian province were diagnosed with a mystery brain disease. What would it mean for the patients if the disease was never real?

In early 2019, health officials in New Brunswick, a small Canadian province, began noticing cases of an extremely rare brain condition called Creutzfeldt-Jakob Disease (CJD). Given CJD’s fatal and potentially transmissible nature, experts quickly gathered to investigate. Thankfully, no further cases emerged at that point, but this was just the beginning of something larger.

Among the team was Alier Marrero, a neurologist from Cuba who had lived in New Brunswick for several years. He relayed troubling news: some patients, including young individuals exhibiting rapid onset dementia, were presenting symptoms reminiscent of CJD. Marrero recorded over 20 cases, with several fatalities, yet tests linked to the CJD Surveillance System consistently returned negative. This left him perplexed.

He noted a frightening variety of symptoms among his patients—dementia, weight loss, jerky movements, facial twitches, and more. Some endured insomnia or vivid hallucinations, while others believed close ones had been replaced by imposters. It was a surreal situation; Marrero conducted countless tests but couldn’t find conclusive answers. “I kept documenting new cases and I kept seeing new people dying,” he reflected. “The image of a cluster became clearer.”

Over time, Marrero and the CJDSS team increasingly worried that they might be dealing with an entirely new and unrecognized brain disease affecting many people in New Brunswick.

As the years passed, his cluster of cases swelled dramatically from 20 to a staggering 500. However, rather than unveiling a new neurological condition, a pivotal research paper released last year suggested that the patients had likely suffered from known neurological or psychiatric disorders. The article described the New Brunswick cluster as a “house of cards.”

To cover this unfolding saga, the BBC spent time with Marrero, his patients, and various officials while examining numerous documents. It was revealed that at least one patient chose medically assisted dying, citing an “unknown degenerative neurological condition” on their death certificate. Another patient considered this option.

Despite the paper concluding there was no new mystery disease, many patients vehemently disagreed, rallying around Marrero and labeling the paper as faulty. They claimed industrial toxins had poisoned them and accused the provincial government of a cover-up.

“I don’t typically think in conspiracy terms, but this seems financially motivated,” remarked Jillian Lucas, one of the patients affected.

Lucas first connected with Marrero in early 2020 after her stepfather, Derek Cuthbertson, began experiencing severe cognitive changes. She quickly found herself facing her own array of baffling symptoms, which Marrero diligently documented.

Despite the exhaustive testing and proactive follow-ups, answers remained elusive. Marrero’s compassion stood out, as he participated closely in his patients’ struggles, offering them solace amid their confusion.

Then, in March 2021, New Brunswick’s chief medical officer sent out a memo to alert local doctors about the emerging crisis. News began to circulate, placing Marrero and his cluster in the limelight. Scientists from across Canada flocked to investigate what seemed like a neurological anomaly.

Amid this storm, much of the focus centered on environmental links. As some patients pointed to the use of glyphosate in forestry, Marrero also found troubling levels of heavy metals in some patients. By April 2021, there was a push for an in-depth environmental inquiry, but New Brunswick abruptly halted cooperation with federal scientists, effectively dousing hopes for critical investigation.

As the provincial government conducted parallel reviews of the initial cases, the conclusions suggested no overarching environmental cause, further infuriating patients who felt their experiences were dismissed.

Frustration marinated in conjunction with the aforementioned investigations as Marrero’s methods began facing scrutiny. Much of the medical community turned cynical, arguing that many patients were being misdiagnosed and failing to receive appropriate care. This sentiment rang true for patients like Lucas, who felt abandoned in a bewildering maze of uncertainty.

Marrero remained committed, referencing his patients and their plight multiple times. As more were diagnosed, he was ultimately removed from the Mind Clinic. The patients faced a stark choice: stay at the clinic or follow Marrero into the unknown.

Most chose to follow Marrero, maintaining their faith in his approach. But he found himself increasingly isolated, with the community still spinning tales about the so-called mystery disease while questions loomed large.

As the wait for clear answers dragged on, Lucas, much like others, considered medically assisted dying—a signal of control amid uncontrollable circumstances. She shared this heavy decision with Marrero, witnessing an emotional response that mirrored her own grief.

Marrero’s path, once shining brightly with prospects, now felt tarnished, yet he continued to fight alongside his patients. “As I result, I kept going because I know I’m not done yet,” he stated resolutely. It’s a complex situation, intertwined with human tenacity, contrasting emotions, and unanswered questions, all while lives hang in the balance.