In 2017, Donald Trump accused Cuba of perpetrating unspecified attacks causing these symptoms. The U.S. reduced staff at their embassy to a minimum in response.[14] In 2018, U.S. diplomats in Chinareported problems similar to those reported in Cuba, as did undercover CIA agents working in other countries with partner agencies to counter Russiancovert operations.[15][16]
Subsequent studies of the affected diplomats in Cuba, published in the journal JAMA in 2018, found evidence that the diplomats experienced some form of brain injury, but did not determine the cause of the injuries.[17][18] While there is no expert consensus on the cause of the symptoms,[7] a co-author of the JAMA study considered microwave weapons to be "a main suspect" for the phenomenon.[3][19] U.S. National Academies of Sciences, Engineering, and Medicine expert committee concluded in December 2020 that microwave energy (specifically, directed pulsed RF energy) "appears to be the most plausible mechanism in explaining these cases among those that the committee considered" but that "each possible cause remains speculative."[20][2][4]
The U.S. intelligence services have not reached a consensus or formal determination on the cause of the Havana syndrome, but unnamed sources in intelligence and two presidential administrations have expressed suspicions to the press that Russian military intelligence is responsible.[21][22]