It's possible it's a side effect of something else. Maybe they are using directed microwaves to power eavesdropping equipment, and the individuals in proximity to that equipment are getting sick.
Since the reported attacks generally happen within a radius of US locations requiring physical security - and apparently not in any other location.
It's otherwise difficult to explain why the USA would be the singular target of these alleged attacks, for a period stretching across decades.
When you start paying attention to these stories, it becomes clear that these secrets are kept first and foremost from the general public of the native countries, mostly for both public image and non-accountability privilege. It makes no sense to deny something that has been known to secret services of every developed country otherwise. It's quite ironic that before Snowden, military insurgents trained by this or that superpower, and mafia bosses who hired ex-special-agents had a more clear picture on, say, phone surveillance than law-abiding citizens.