Most ‘Havana Syndrome’ Cases Unlikely Caused by Foreign Power, C.I.A. Says

The agency has never accused Russia or another power of being responsible, but some officials, particularly in the Pentagon, said they believed there was evidence of the involvement of Moscow’s spy agencies, and many victims concurred. When Mr. Burns traveled to Moscow in December to warn Russia against invading Ukraine, he raised the issue of the health incidents and said if Russia was found responsible, there would be consequences.

Marc Polymeropoulos, a former C.I.A. officer who suffered Havana syndrome symptoms on a trip to Moscow in 2017, said it was critical to continue to investigate the cases that remain unexplained. Praising Mr. Burns’s efforts to improve care for injured officers, he added that the C.I.A. should not revert to a culture where victims were denigrated and dismissed.

“It took us 10 years to find Osama bin Laden,” Mr. Polymeropoulos said. “I would just urge patience and continued investigation by the intelligence community and the Department of Defense.”

Another victim, who asked that his name not be used because of his work for the agency, said the government had erred by pushing for more people to report ill health or unexplained symptoms. That brought in thousands of extraneous cases, the victim said, making it harder for the agency’s analysts to focus on the real cases.

The government official briefed on the findings said the effort to bring in large numbers of reports was not a mistake because it allowed the United States to speed up treatment for people suffering from symptoms. The effort also helped provide needed treatment to people with previously undiagnosed conditions, officials said.

C.I.A. officials said there was agreement within the intelligence community about the finding that the majority of Havana syndrome incidents were not the work of an adversarial power conducting a sustained campaign around the globe. Still, confidence in that assessment ranged from low to high across various intelligence agencies.

In addition to the C.I.A., an expert panel has been looking at classified information about the incidents. The panel, which has provided its findings to the government but is still finishing its report, explored technologies that could result, at least theoretically, in the symptoms being reported.