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One of the weirdest medical tales to unravel in recent years—the wave of U.S. and Canadian diplomats in Cuba stricken by unexplained, concussion-like symptoms as well as hearing loss—has taken another turn. A group of researchers in Canada say they’ve found evidence that pesticides, not sonic energy weapons, might be to blame for sufferers’ agony.




Much of the attention over the mysterious ailment, now known as “Havana syndrome,” has focused on the U.S. diplomats and their families who first became ill in 2016. Some of these patients are said to have heard strange noises right before their symptoms emerged, which led to speculation by some scientists and even U.S. officials that they had been attacked by exotic, possibly sonic weapons—alleged attacks that some speculated were instigated or aided by Cuba.

The Cuban government has disavowed any responsibility for these cases as well as shut down the sonic weapon theory. And despite some very disputed, U.S. government-sponsored research suggesting that Havana syndrome patients have experienced unique brain changes that could have been caused by something unprecedented like a new weapon, there still isn’t any concrete, single explanation for what may have happened to the dozens who reported symptoms.


Like the U.S., Canada has been conducting their own investigation of the syndrome in their diplomats, with the help of outside researchers. But they’ve come to very different conclusions. Last week, Radio-Canada’s investigative TV program Enquête obtained a draft copy of the study, which has yet to be published in a peer-reviewed journal. On Tuesday, the lead author of the study, Alon Friedman, a neuroscientist at Dalhousie University, spoke to Buzzfeed News about the preliminary results.

“We actually found a specific brain region that was affected and that was the clue to everything else,” Friedman told Buzzfeed News.

Friedman and his team compared Canadian patients who were given an extensive medical check-up soon after they returned from Havana to those who were studied one to 19 months later, as well to a control group of unaffected people who never lived in Havana. Some were also tested twice, before and after their trips to Havana.




One of the clearest differences was that few Canadian patients reported hearing any strange sounds before their symptoms occurred, while no one reported any hearing loss. But the brains of some patients did show signs of damage in regions that process an enzyme called cholinesterase, including regions like the brain stem that help regulate our sense of consciousness and sleep.

There’s a shortlist of neurotoxins that are known to affect these regions and disturb the processing of cholinesterase, the authors wrote, and they include several types of pesticides. Sure enough, they found some of these pesticides in people’s systems. When they looked at fumigation records for the Havana embassy, they also saw there had been increased spraying in response to the mosquito-spread Zika virus, which at the time had recently emerged in the Americas for the first time ever. And perhaps most importantly, there was also a link between those who got the sickest and those whose homes had been fumigated the most.


The team’s theory is admittedly based on circumstantial evidence. And according to Douglas Fields, a neuroscientist who has independently investigated the cases, there’s still the possibility that more than one natural cause may ultimately explain these patients’ symptoms. In fact, given how the cases among affected Canadians are so different from the U.S. cases in presentation, it’d be strange if the answer didn’t turn out to be multiple choice. But at the very least, it’s a theory that can be further studied without delving into the world of Tom Clancy.

“The pesticide theory is plausible but not proven, and the study has many weaknesses,” Fields told Gizmodo via email. “However, it’s good to see this attempt at a reasonable diagnosis, instead of the past approach of assuming the existence of a new energy beam neuroweapon. This paper is not the last word.”


According to Buzzfeed News, officials in both the U.S. and Cuba are looking into the new findings and remain in communication with the Canadian government.