A United States Government employee in southern China has reported suffering from "abnormal" sounds and pressure leading to a mild brain injury, the USA embassy said - recalling similar experiences among American diplomats in Cuba.
Both the US State Department and the Chinese government were investigating the incident, the embassy said.
USA officials have issued a health alert in China following the incident. The U.S. also expelled 15 Cuban officials from its embassy in Washington. That evaluation found that the employee's symptoms were similar to those of someone with a head concussion or mild traumatic brain injury.
The employee experienced the symptoms from late 2017 through April 2018 while on assignment in the southern Chinese city of Guangzhou, where a US consulate is located, according to Jinnie Lee, a spokeswoman at the USA embassy in Beijing.
The suspected "sonic attack" has been linked to "medically similar" episodes experienced by U.S. government staff in communist Cuba in late 2016.More news: China relieved as trade tensions ease
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"The department is taking this incident very seriously and is working to determine the cause and impact of the incident", said Nauert.
China's Foreign Ministry did not immediately respond to a request for comment.
In Cuba, the American victims had associated the onset of their symptoms with "unusual sounds or auditory sensations". State Department said in its health advisory posted online Wednesday.
"The U.S. government is taking these reports seriously and has informed its official staff in China of this event", the embassy said in a statement.
Officials initially suspected the Americans had been targeted by an acoustic weapon, but media reports have suggested that the Federal Bureau of Investigation has been unable to verify any evidence to support that theory. "Various descriptions were given: "a high-pitched beam of sound"; an "incapacitating sound"; a "baffling sensation" akin to driving with the windows partially open in a vehicle; or just an intense pressure in one ear". "Instead, move to a location where the sounds are not present", the alert advised.
Despite hundreds of billions of dollars in annual trade between them, China and the US are considered strategic rivals for influence in Asia. Previous victims of similar attacks in Cuba suffered permanent hearing loss, severe headaches, loss of balance, brain swelling, and disruption to cognitive functions.