Several comments are assuming the goal of the secret method is making someone sick. But as others have said, becoming sick may be a symptom of exposure, so the

Several comments are assuming the goal of the secret method is making someone sick. But as others have said, becoming sick may be a symptom of exposure, so the intended purpose is something else like surveillance. Here’s the problem though, this genie is already out of the bottle, even if something like this didn’t exist and the Havana syndrome is mass psychosis, someone I am sure is busy making a directed-energy surveillance mechanism because the “enemy may do it first”. Isn’t it possible to know what’s going on in the environment though, for example by using a spectrum analyzer, or detection methods for ultrasound?