The matter first came to light in 2017, when Washington recalled the majority of its personnel from its embassy in Havana, Cuba, and at least two more diplomats from its consulate in the Chinese city of Guangzhou. The evacuees reported experiencing “unusual acute auditory or sensory phenomena” and hearing “unusual sounds or piercing noises”. Subsequent tests showed that the diplomats suffered from sudden and unexplained loss of hearing, and possibly from various forms of brain injury. In the most recent known case, “about two dozen” personnel at the US embassy in Vienna showed Havana syndrome symptoms in the first half of 2021.

But now a study by the CIA has concluded that the vast majority of Havana syndrome cases could be “explained by environmental causes, undiagnosed medical conditions or stress”. The study, described as “comprehensive” by CIA sources, supports the view that environmental causes, rather than “a sustained global campaign by a foreign power”, could explain most Havana syndrome cases. According to The Times, the conclusion of the CIA study is broadly shared by other members of the United States intelligence community, though confidence levels vary.

The Director of the CIA, William Burns, said yesterday that the agency had “reached some significant interim findings”, but would continue to investigate the Havana syndrome, given that two dozen cases remained difficult to explain. However, the conclusions of the study appear to have displeased many victims, according to The Times. One organized group of victims described the CIA study as “interim” and said that its results “cannot and must not be the final word on the matter”.