In 2016, Central Intelligence Agency employees stationed in Cuba started reporting something strange. They began experiencing intense headaches, ringing in their ears and fatigue. For some people, it was even worse, with cases of brain damage and cognitive function being reported.

Since then, there have been 1,000 reported cases of the mysterious illness now known as Havana syndrome. Some people have speculated it was caused by a secret sonic weapon deployed by another geopolitical power, while others claimed it was a mass psychogenic illness. Kevin Fu, an electrical and computer engineering professor at Northeastern University, says the real cause is probably something simpler: crickets.

“The greatest contender right now is the short-tailed West Indies cricket, which has a chirp that’s extremely annoying to the point where it can cause harm to you,” Fu says. “That’s the theory I’d put my money on, but it’s still unsolved. In my opinion, it’s not likely it’s a nation state trying to deliberately cause harm.”

With his experience in the “dark arts of electronic warfare,” Fu appeared on the most recent episode of History Channel’s “History’s Greatest Mysteries” focused on Havana syndrome. In 2018, Fu performed experiments with ultrasound that showed how Havana syndrome could be the result of “malfunctioning ultrasonic eavesdropping devices.”

But since that time, Fu has come around to the cricket theory––and he’s not alone. In a declassified report, JASON, an advisory group that works with the State Department, also found reason to believe that the Indies short-tailed cricket could be the culprit. The group performed a pulse repetition analysis of audio captured in Cuba and audio of these crickets and found they were remarkably similar.

“The chance of that being randomly the same is zero,” says Fu, who was recently appointed to the White House’s working group on cybersecurity resilience. 

“That was convincing enough, but then on top of that, it’s a really simple explanation,” Fu continues. “It explains all the symptoms, whereas all the other approaches really require a healthy dose of imagination.”

After several investigations, the CIA made the assessment in 2022 that the mysterious illness was not caused by a “sustained global campaign by a hostile power.” It might provide some peace of mind that “it appears to be more of an industrial, environmental issue than some kind of ill intent,” Fu says. But even the cricket theory is still a theory, he admits. The real cause of Havana syndrome remains a mystery. 

“It’s sad that it’s not solved because there are real people that were harmed,” Fu says. “Even in the absence of a nation state, it doesn’t mean they’re making it up––this is real.”

Cody Mello-Klein is a Northeastern Global News reporter. Email him at c.mello-klein@northeastern.edu. Follow him on X/Twitter @Proelectioneer.