At least four other US diplomats have shown symptoms of the mysterious "Havana Syndrome" while in Europe, the Wall Street Journal reveals.
According to the newspaper sources, at least three cases were reported last year by members of the US mission in Geneva, and at least one of the diplomats was transported to the US for treatment. A suspicious incident took place around the same time in Paris.
About 200 US officials around the world have so far reported "abnormal health incidents", as the US government calls the unexplained phenomenon, which was first reported in 2016 at the US Embassy in Havana, Cuba.
Neurological symptoms
Affected officials experienced headaches, dizziness, memory loss and persistent concussion-like symptoms, and many claimed to have heard strange, loud noises before the sudden onset of symptoms. Some were diagnosed with brain damage.
In November, the FBI announced that it was investigating the matter as a "top priority."
Attacks with "sound weapons", mass hysteria, malfunction of spy devices, are some of the theories that have been put on the table, but none have been confirmed.
Last year, however, a report by the American National Academy of Sciences concluded that the strange symptoms could have been caused by "directed microwaves", although the authors avoided talking about deliberate attacks.
Cases have been reported in US services in Germany, Colombia, Russia and Austria, and a similar incident reportedly led to the postponement of US Vice President Kamala Harris's trip to Vietnam last August.
About half of the cases involved CIA employees, the director of the service, William Burns, stated in July last year.
The State Department declined to comment on the Wall Street Journal report, but Secretary of State Anthony Blinken told MSNBC that every effort was being made to unravel the mystery and identify the "culprits."