In 2017 Washington recalled the majority of its personnel from the US embassy in Havana, and at least two more diplomats from the US 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 they suffered from sudden and unexplained loss of hearing, and possibly from various forms of brain injuries. In April of 2019 the Canadian embassy evacuated all family members of its personnel stationed in the Cuban capital over similar health concerns.

The latest study by the National Academies of Sciences resulted from the coordination of leading toxicologists, epidemiologists, electrical engineers and neurologists. The resulting 66-page report describes in detail the symptoms experienced by nearly 40 US government employees, who were examined for the purposes of the study. Its authors said they examined numerous potential causes, including psychological factors, infectious diseases, directed radio frequency energy, and even exposure to insecticides. Ultimately, the authors concluded that “many of the distinctive and acute signs, symptoms and observations reported by [US government] employees are consistent with the effects of directed, pulsed radio frequency (RF) energy”, according to their report.

However, the study does not attempt to answer the burning question of whether the symptoms experienced by the sufferers resulted from deliberate attacks, and if so, who may have been behind them. Some have accused the governments of Cuba and/or Russia of being responsible for the syndrome. However, the Cuban and Russian governments have strongly denied the accusations. The National Academies of Sciences report does state that the systematic study of pulsed radio frequency energy has a history of over half a century in Russia and the Soviet Union.