For more than 18 months, US diplomats have come down with similar illnesses that include mild brain damage and hearing loss after they claim to have heard unusual sounds. The incidents began in Cuba but reports have now spread to other countries. As authorities have ramped up efforts to treat any potential cases, almost 200 people have reportedly come forward to be tested.
GIF: Getty, Sound Waves Wikia
The US State Department has had little to say about the incidents that began in Havana in the spring of 2016, and the resulting information vacuum that has left the door wide open for conspiracy theories and other unverified claims.
For now, no one can say for certain what is happening in these cases, but it appears US diplomats are being targeted in some sort of attack that's left experts baffled. In the beginning, officials believed that some unknown "sonic device" was being used against the victims, but other theories have emerged in the meantime.
Some American diplomats reported hearing strange sounds, of which an audio recording was later released to the public. Symptoms varied between victims but the list included "hearing loss, dizziness, tinnitus, balance problems, visual difficulties, headaches, fatigue, cognitive issues and sleeping difficulties".
Since then, we've seen reports of diplomats falling ill in China.
On Tuesday, the Associated Press reported that 26 Americans have been "medically confirmed" to have been injured in wave of incidents, and diplomats who have served in at least seven cities in four countries have sought testing.
Nearly 200 employees from the US diplomatic mission and their family members have elected to take part in a new screening program that US officials, speaking anonymously, told the AP is part of "an abundance of caution".
Of those Americans, fewer than a dozen were said to have been transported to the University of Pennsylvania in Philadelphia for further review by medical professionals.
The AP described a previously unreported incident that had officials worried about President Trump's recent visit with Kim Jong-Un:
As President Donald Trump was heading to Singapore for a historic summit with North Korea's leader, a State Department diplomatic security agent who was part of the advance team reported hearing an unusual sound he believed was similar to what was experienced by US diplomats in Cuba and China who later became ill.
The agent immediately underwent medical screening - part of a new US government protocol established to respond to such potential health incidents anywhere in the world. And while the president was flying to the Southeast Asian city state, the US delegation preparing for his arrival was exchanging urgent messages with the State Department headquarters back in Washington, including the agency's Diplomatic Security and the US Secret Service.
Four US officials told the AP that it turned out to be a false alarm, but there is a heightened awareness among security officials as the White House prepares to meet with Russia's president Vladimir Putin next month.
Suspicions of Russian involvement in the attacks were raised last September when an unnamed USAID officer and his wife were flown out of Tashkent, Uzbekistan for evaluation after they reported events that echoed what happened in Havana. The US State Department later said that it isn't "going to discuss every case individually", but "We can confirm that there was no incident in Uzbekistan".
At this point the only medically confirmed cases have occurred with diplomats stationed in Cuba and one stationed in China.
The US has issued an alert warning Americans travelling to China to seek medical attention if they experience "auditory or sensory phenomena" similar to what was reported in Havana, and the US State Department recommended anyone travelling to Cuba should "reconsider" their plans.
Since reporters first blindsided spokesperson Heather Nauert with questions about the incidents last August, the US State Department has been reluctant to give on-the-record details about its investigation. It still refers to these cases as "specific attacks" without saying what is specifically happening.
We've seen numerous theories for what could cause these kinds of symptoms floated over the last year, including weaponised microwaves or radio waves and malfunctioning surveillance gear. The fact that they don't know how the attacks occur tends to obscure the fact that we don't know why they're occurring in the first place.
What does seem to be clear is that authorities are so concerned that they're rushing to address any potential incident that arises. And the longer the mystery goes on, US diplomats abroad are only more susceptible to private fears that they may be a victim.