Four years ago, dozens of American officials stationed in Cuba started to hear odd cracks and humming in their ears – punctured by rushes of nausea, headaches, cloudy vision, memory loss, disequilibrium, and lethargy – all critical indicators of mild traumatic brain injury (TBI).

The phenomenon was quickly dubbed the "Havana syndrome." And while similar symptoms have been documented by U.S. government employees in other places abroad, reports emerged this week suggesting that the potential sonic attacks might be far more pervasive than what was publicly known. In turn, more fingers are pointing toward Russia as being behind the global barrage of possible sonic attacks.

"There are a number of Americans who have fallen ill now, and we need to know why and who is behind it," Dan Hoffman, a former CIA Moscow bureau chief who retired in early 2017, just before the strange illnesses began, told Fox News. "This is something worthy of a congressional hearing."

In this Nov. 10, 2019, photo, tourists take a joy ride along the malecon sea wall in Havana, Cuba. The city of Havana celebrated its 500th anniversary on Nov. 16. (AP Photo/Ramon Espinosa)

In this Nov. 10, 2019, photo, tourists take a joy ride along the malecon sea wall in Havana, Cuba. The city of Havana celebrated its 500th anniversary on Nov. 16. (AP Photo/Ramon Espinosa)

According to former high-ranking CIA officer Marc Polymeropoulos, a late 2017 Moscow trip – amid the calamity of the Russian election interference findings put forth by the U.S. intelligence community – came to an unpleasant end when he was riddled with vomiting and vertigo that persisted long after he returned home, G.Q. reported.

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His ailments oddly lined up with those disclosed not only a year earlier in the newly-rehabilitated U.S. Embassy in Havana, but what would also start to unravel in China in 2018.

In June that year, U.S. government staffers and intelligence officials in Guangzhou working specifically on Russian influence issues were sent back stateside following increasing anecdotes of illness and fatigue. Some said the onset of sickness also befell family members and began in late 2017.

"The safety and security of U.S. personnel, their families and U.S. citizens is our top priority," a statement from the U.S. State Department read at the time. "The U.S. government has not yet determined a cause or an actor."

Russian President Vladimir Putin attends a cabinet meeting at the Novo-Ogaryovo residence outside Moscow, Russia, Tuesday, Aug. 11, 2020. (Alexei Nikolsky, Sputnik, Kremlin Pool Photo via AP)

Russian President Vladimir Putin attends a cabinet meeting at the Novo-Ogaryovo residence outside Moscow, Russia, Tuesday, Aug. 11, 2020. (Alexei Nikolsky, Sputnik, Kremlin Pool Photo via AP)

While the administration did also launch an investigation concerning the matter in Cuba, withdrew the majority of its staffers coupled with a travel advisory, framed the happenings as "targeted attacks," and expelled 15 Cuban diplomats from Washington, no real evidence of Cuban wrongdoing ever surfaced. Moreover, no hardline findings were ever brought to bear on the strange occurrences and dull pings. Canadian officials have also since withdrawn 14 citizens from Havana, citing eerily akin neurological conditions. 

Yet the peculiarities continue to pile up with few definitive answers. Then in November last year, as per GQ, an unnamed White House staffer was additionally targeted by a man who exited a parked van and passed the staffer as she walked her dog in Arlington, Va. She later informed officials that she was riddled with intense headaches and face prickling, and even her canine companion started suffering from a sudden seizure.

In a separate case months earlier, an unnamed American diplomat and his family purportedly heard similar mysterious sounds and fell ill while stationed in Philadelphia. Both the diplomat and his wife reported feeling pressure in their head before finding their children moving bizarrely and "in unison" in their sleep, GQ reported.

"Sonic devices concentrate sound waves into a narrow cone of sound, extending about 15 degrees in every direction from the axis," explained John Wood, a defense analyst and author of "Russia, the Asymmetric Threat to the United States." "This 'directional sound wave' focuses kinetic energy into a tight space. It is, therefore, an effective sound canon designed to disorientate and debilitate the hearer and disperse a crowd."

The anomalies have since surfaced in a slew of other countries ranging from Poland and Georgia to Taiwan and Australia, raising red flags over what covert weapons might be directed at U.S. personnel, and more scrutiny is turning to Moscow as a likely culprit.

According to Wood, it is not yet evident that the attacks are related – but they are consistent with the employment of a sonic device.

"At both the civilian and military level, Russia has used such weapons against protesters and U.S. diplomats," he said.

Hoffman also pointed out that such attacks, while generally not deemed life-threatening but certainly damaging and injurious, would be borne out of a desire to drive a wedge between the U.S. and other countries and "mark up the cost" for a diplomat and their family serving American interests.

A large American flag is unfurled at the Pentagon (AP Photo/J. Scott Applewhite)

A large American flag is unfurled at the Pentagon (AP Photo/J. Scott Applewhite)

But complicating the U.S. government probe is the vast array of differing prognostics and experiences. Some reports have pointed to individuals in either homes or hotels hearing high-pitched tones or jarring thuds from one direction or all around. Some endure a kind of tremoring or a wind-like pressure; some hear nothing at all.

The New York Times this week underscored that the "most compelling evidence" implicating Moscow stems from publicly available data in which CIA investigators were able to access location information from private companies, and affirmed that in each sonic-like case in 2019, "individuals believed to be FSB (Russian) agents were within the range of the CIA officers who had been hit."

U.S. Secretary of State Mike Pompeo said Wednesday that the mysterious maladies are still under review and dismissed claims that American workers were not adequately protected. The CIA has also rebuffed claims of neglect.

The Russian Embassy told Fox News that the "insinuation of Moscow's involvement is "absolutely absurd and bizarre," – but experts are quick to point to a sobering history.

Matthew Schmidt, national security and political science coordinator at the University of New Haven, emphasized that these apparent attacks bear the markings of a Soviet-style electromagnetic attack on the U.S. Embassy in Moscow in the '60s and '70s, and the "Moscow Signal" microwave incidents.

"The present-day incidents fit that pattern, and the fact that we've seen similar incidents [with] U.S. employees working in China and Cuba, Russia's close allies, bolsters the case," he conjectured. "Generally, the idea is just to break the rules of the game, which normally say rival intel services don't cause physical harm. That destabilizes the game. People are worried, people don't perform as well because they're sick, or they're worried about being hurt and taking precautions against it, which may make them less effective."

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John Hardie, a Russian foreign policy specialist at the Foundation for Defense of Democracies (FDD), concurred that during the height of the Cold War, the Soviet intelligence services likewise "used methods that endangered the health and well-being of American diplomats and intelligence officers, such as beaming concentrated electronic pulses and microwaves to eavesdrop on the U.S. Embassy in Moscow carcinogenic 'spy dust' used to track U.S. intelligence officers."

However, since relations between the two rivals were restored in the aftermath of the Soviet Union's collapse, there has been a longstanding rule of conduct between the Russian and U.S. intelligence services that they do not do physical harm to one another's officers if it can be avoided.

("But) these reports seem to indicate a new and different practice," observed Matthew Rojansky, Director of the Kennan Institute at the Woodrow Wilson International Center for Scholars and adjunct lecturer at the Paul H. Nitze School of Advanced International Studies at Johns Hopkins University. "This is not a brand new technology, but the weaponization of it in this particular way is fairly novel. So it's hard to say that it clearly has a Russian signature, but it seems to have Russian hallmarks."

Still, neither the cause nor the authority behind the evolving "Havana Phenomenon" remains subject to speculation, and what remains unclear is just how many Americans have been impacted, although around 60 are said to have been treated by experts at the Center for Brain Injury and Repair at the University of Pennsylvania.

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Several sources connected to the CIA told Fox News that the attacks do and are warranting magnified concern.

"This type of sonic attack will create immediate debilitating effects in its target and long-term health effects. So it can be used for tactical or strategic purposes, for short-term distraction or debilitation or long-term psychological or political effects," added Nick Dowling, a defense fellow at the National Defense University as well as a two-time policy adviser for presidential campaigns. "We should also consider how an adversary might use this technology in a more direct attack. A sonic attack could be used to degrade if not debilitate military or police formations or render civilian areas impossible to enter, for all those without proper ear protection."