More US diplomats, employees, and their families in China are being medically evaluated and evacuated amid growing accounts of mysterious episodes involving sound and pressure that appear linked to the development of mild traumatic brain injuries, according to reports by The New York Times.

Last month, the State Department revealed that one US employee at the US consulate in the city of Guangzhou, just northwest of Hong Kong, reported experiencing “ subtle and vague, but abnormal, sensations of sound and pressure ” and sustained a mild traumatic brain injury despite no evidence of a blow to the head. The episode drew eerie parallels to the mysterious “health attacks” experienced by diplomats at the US embassy in Cuba, which left 24 Americans with similar brain injuries.

That unidentified employee in Guangzhou was evacuated and sent for more medical testing in the US. The State Department, meanwhile, issued a health alert on May 23 for those remaining in China. Though the department suggested vigilance, it added that it was “not aware of any similar situations in China, either inside or outside of the diplomatic community,” suggesting that the episode may have been an isolated event so far.

But in an interview with the Times, Mark Lenzi, an American security engineering officer at the Guangzhou consulate, disputed that suggestion. “They knew full well it wasn’t [an isolated case],” he said.

He, his wife, and two children were evacuated on Wednesday, June 6. He said that he and his wife had suffered unexplained headaches and sleeping problems since the end of last year—about the same time the first, unidentified evacuated employee reported experiencing problems. The couple also reported unexplained sounds, similar to marbles rolling around a metal funnel.

Since the health alert, more employees have come forward reporting such noise episodes and symptoms, including, “dizziness, headaches, tinnitus, fatigue, cognitive issues, visual problems, ear complaints and hearing loss, and difficulty sleeping,” according to the State Department. Those symptoms are generally consistent with those of a mild traumatic brain injury.

On May 31, a medical team and specialists from the Centers for Disease Control and Prevention arrived in Guangzhou and began screening some of the more than 100 employees at the consulate.

Fear and flight

In a statement released to the press late Wednesday, State Department spokesperson Heather Nauert said:

As a result of the screening process so far, the department has sent a number of individuals for further evaluation and a comprehensive assessment of their symptoms and findings in the United States.

The department would not reveal the counts of those screened and evacuated so far, but one official told the Times that a “sizable number” of people working in Guangzhou had requested screening.

For a “town-hall”-style meeting that took place Tuesday, June 5, acting Director General of the Foreign Service William E. Todd flew in to Guangzhou to discuss medical evacuations with employees, among other things.

Those evacuated are being sent for further evaluation at the University of Pennsylvania Center for Brain Injury and Repair, where a team of doctors conducted in-depth clinical exams on 21 Americans affected by similar episodes in Cuba . In those cases, the team determined that the victims had sustained “injury to widespread brain networks without an associated history of head trauma.” Their results were published in March in JAMA

So far, there are no leading hypotheses for what is causing the sounds and brain injuries, despite rampant discussion of “sonic attacks,” as well as malfunctioning surveillance equipment. As Ars has noted before, it’s unlikely that audible sounds or even infrasound alone could cause such brain injuries—particularly without large, hard-to-conceal sonic equipment, like massive speakers, being noticed by victims. A team of researchers proposed that ultrasonic interference from devices such as room-occupancy sensors could explain the noises people report. But again, there’s no evidence or clear hypothesis for this causing the constellation of symptoms and brain injuries seen in victims.

High-intensity, focused ultrasounds (>20,000Hz) can cause brain tissue heating and damage. But, as Joseph Pompei, a former MIT researcher and psychoacoustics expert told the AP earlier, "somebody would have to submerge their head into a pool lined with very powerful ultrasound transducers” to sustain a brain injury.

As the team of doctors speculated in their JAMA report, the sounds may be merely associated with the harmful phenomena, not the cause of injuries. Other guesses as to the cause include collective delusions, toxins, and infectious agents.

On Thursday, June 7, the Chinese Foreign Ministry said it was prepared to aid the US in investigating the mysterious episodes.