The unnamed employee in the city of Guangzhou "recently reported subtle and vague, but abnormal, sensations of sound and pressure", the State Department said in an emailed statement to USA citizens in China.
The US originally called the Cuba incidents "sonic attacks", but later backed off that phrasing as medical experts examined the patients and found their symptoms and conditions of mysterious origins.
"The US government is taking these reports seriously and has informed its official staff in China of this event", the statement added about the symptoms, which occurred from late a year ago to April.
"The Chinese government has assured us they are also investigating and taking appropriate measures", she said.
The embassy's health alert says the government employee "recently reported subtle and vague, but abnormal, sensations of sound and pressure".
In October, a State Department official said the USA had "received a handful of reports from US citizens who report they experienced similar symptoms following stays in Cuba".
The embassy warned workers in China to move away from the source of the noise if they experience "any unusual acute auditory or sensory phenomenon" with "unusual sounds of piercing noises".
The unnamed American citizen assigned to the consulate in Guangzhou had reported a variety of "physical symptoms" dating from late 2017 to April this year, the US embassy in Beijing said in an email. Ten Canadian diplomats and their relatives also suffered a odd illness.
"We can not at this time connect it with what happened in Havana, but we are investigating all possibilities", a U.S. embassy official told Reuters.
A spokesperson at the U.S. Embassy in Beijing confirmed to CBS News that from late 2017 through April 2018, a U.S. government employee assigned to the Guangzhou Consulate reported "a variety of physical symptoms".
An expert panel set up by the State Department previous year said the initial findings were most likely related to "neurotrauma from a non-natural source" and recommended further investigation.
The diplomats described concussion-like symptoms like hearing loss, dizziness, balance problems, visual complaints, headaches, fatigue, cognitive issues and difficulty sleeping. -Cuban relations, while investigators have chased theories including a sonic attack, electromagnetic weapon or a flawed spying device.
Then-Secretary of State Rex Tillerson said in October that the US was expelling the diplomats because of Cuba's "failure to take appropriate steps to protect our diplomats" in Havana.
"The cause (of their symptoms) remains unknown but could be human-made", the Canadian government concluded.
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