I've been following this intermittently since... 2016 or so? The part that's strange is why does it seem to only affect State Department employees and others in similar roles? If it were environmental factor, cases would likely be occurring among a wider group. And if it is just that group, the only two causes that seem likely are some sort of toxic exposure during employee training, which seems implausible for the State Department, or that an organized group is being the syndrome.
Five of seven U.S. intelligence agencies may say there isn't a state-based actor behind Havana Syndrome, but I've yet to see an evidence-based alternative proposed. From
CNN's article on that report:
Intelligence officers vigorously studied what happened in the hours, days and weeks surrounding the incidents, the official explained.
In some instances they found malfunctioning HVAC systems, which can cause discomfort to humans, and in other cases there were computer mice that created surprising disruptions.
“We weren’t finding what we expected to find,” said one of the US officials. “There is no one explanation for any of this.”
Computer mice behind these syndromes? Which brand is selling mice that are so far out of electromagnetic regulations that they can cause this sort of syndrome? Particularly with the sudden onset? And if it's HVAC systems, why isn't this identifiable as some sort of e.g. refrigerant poisoning that also crops up occasionally in other occupations? In both cases, can we not at least have a summary of the causes, e.g. 12.3% of the cases are due to HVAC systems that have this type of flaw?
I see two recent government reports on the topic.
This one (2023 Updated Assessment) is the one the CNN article is predicated on, along with their interviews with the computer mouse theorist, among others. There's also this
2022 Executive Summary, which contains significant redactions. But they contradict each other in some ways. From the Updated Assessment:
Updated Assessment said:
IC agencies assess that symptoms reported by US personnel were probably the result
of factors that did not involve a foreign adversary, such as preexisting conditions, conventional illnesses, and
environmental factors. IC confidence in this explanation is bolstered by the fact that we identified medical,
environmental, and social factors that plausibly can explain many AHIs reported by US officials...
While initial medical studies concluded AHIs represented a novel medical
syndrome or consistent pattern of injuries similar to traumatic brain injury (TBI), a combination of medical and
academic critiques pointed to methodological limitations in that work
Executive Summary 2022 [Declassified by DNI Avril Haines] said:
Although some signs and symptoms of AHIs are common in known
medical conditions, the combination of the four core characteristics is distinctly unusual and unreported
elsewhere in the medical literature, and so far have not been associated with a specific neurological
abnormality. Several aspects of this unique neurosensory syndrome make it unlikely to be caused by a
functional neurological disorder. The location dependence and sudden onset and offset, for example,
argue for a stimulus that is spatially and temporally discrete. The perception of sound and pain within
only one ear suggests the stimulation of its mechanoreceptors, a specific cranial nerve, or nuclei in the
brainstem, all of which mediate hearing and balance. The lack of other symptoms also helped rule-out
known medical conditions.
So the 2022 Executive Summary says that these combination of symptoms in these "Anomalous Health Incidents" (AHIs) "is distinctly unusual and unreported elsewhere in the medical literature", but the 2023 report says that the intelligence community believes that "preexisting conditions, conventional illnesses, and environmental factors" are the probably cause, and that "we identified medical... factors that can explain many AHIs reported by US officials"?
The 2023 report is quite vague about the findings of these new studies that contradict the 2022 Executive Summary, and does not cite any of them, nor specify
which medical/environmental/social factors are responsible. I'm open to persuasion if there is evidence, but the lack of citations is itself suspicious, and without that data, I'm inclined to still go by the more-specific-despite-its-redactions 2022 summary.