Secretary of State Mike Pompeo said on Wednesday that "the medical indications are very similar and entirely consistent" with the symptoms reported by Americans working at the U.S. Embassy in Cuba.
An American working at the US Consulate in southern China reported experiencing "abnormal" sounds and pressure that resulted in a mild brain injury - reminiscent of a mysterious illness that recently hit diplomats in Cuba, officials said Wednesday.
The diplomats said when they left rooms in the embassy, the symptoms and sounds immediately stopped.
The incident is likely to recall the still unexplained "sonic attacks" on USA diplomats in Cuba.
In Cuba, some two dozen American diplomats and their family members experienced a range of ailments, often after hearing an unusual sound.More news: World Health Organization ships first batch of Ebola vaccine to DR Congo
The health alert issued Wednesday warned US citizens to be vigilant.
The State Department says a USA government employee working in China suffered "subtle and vague, but abnormal, sensations of sound and pressure" that later led to a diagnosis of "mild traumatic brain injury".
The alert said a USA government employee in the southern Chinese city of Guangzhou reported "subtle and vague, but abnormal, sensations of sound and pressure".
Last October, the State Department ordered non-essential embassy personnel and the families of all staff to leave Havana, arguing the USA could not protect them from unexplained illnesses that have harmed at least 24 Americans. "Instead, move to a location where the sounds are not present", recommends the State Department.
CNN has reached out to China's Ministry of Foreign Affairs but has not yet received a response on this matter. State Department spokeswoman Heather Nauert said the United States will send a medical team to Guangzhou next week to conduct baseline medical evaluations of all employees who desire one. The Chinese government has assured the US that it is investigating the matter and taking appropriate measures, according to a State Department spokesperson. Media reports have suggested that the Federal Bureau of Investigation has not been able to verify any evidence to support the sonic weapon theory. Previous victims of similar attacks in Cuba suffered permanent hearing loss, severe headaches, loss of balance, brain swelling, and disruption to cognitive functions.