In late March, the Americans in Cuba were finally told about what was happening to some of their colleagues. Word spread. Within a month, 80 Americans, including staff and family, wanted to be “checked out” by medical professionals. Word spread to the Canadians, too, and they got examined independently.

The older diplomat and his wife “along with 22 other Americans and eight Canadians ... would be diagnosed with a wide array of concussion-like symptoms, ranging from headaches and nausea to hearing loss.”

But note the difference in the number between the number of Americans checked out (80) and those diagnosed with symptoms (22).

Add to that: FBI investigators have found no evidence about what happened, despite being on the ground.

And finally: FBI officials have “privately emphasized the government‘s cooperation with its investigators,” according to ProPublica.

These are just three of the many things that have confounded investigators. Was there a real attack followed up with mass hysteria, once word started to spread? Or was it all mass hysteria? Or all attack? Or ... what?

The core problem is that no one has heard of or is willing to testify to the existence of this kind of acoustic weapon.

There are crowd-control weapons known by the euphemism “Long-Range Acoustic Devices” that are on the market and have been deployed against protesters at various times. But the way they would damage hearing is pretty obvious: They are really, really, really loud.

The facts of the Cuban case are very different. Some people report loud cicada-like noises. Others none at all. Some reported attacks in hotels, where other guests didn’t hear anything, so it would appear the radius of attack is quite small. A focused, long-range acoustic weapon is unknown to the world.

In 2007, Air Force researchers reviewed the research and literature on the topic and came to a solid conclusion. “Although high-intensity infrasound significantly disrupted animal behavior in some experiments, the generation of such energy in a volume large enough to be of practical use is unlikely because of basic physical principles,” they wrote. “On the basis of experimentation completed to date at a number of institutions, it seems unlikely that high-intensity acoustic energy in the audible, infrasonic, or low-frequency range can provide a device suitable for use as a nonlethal weapon.”

The AP has even released recordings of what it says diplomats heard, but that did nothing to further the case.

So, what the hell happened?

Bizarrely, the easiest explanation would be “mass sociogenic illness,” or what used to be called mass hysteria. There are dozens of examples in the extant literature, usually focusing on rumors of poison gases or, in more recent times, terrorist deployment of chemical weapons. The mind may be powerful, but sometimes, subsequent investigation reveals that there was some toxin causing the symptoms, after all.