It reads like a bad spy thriller. Between November 2016 and October 2017, a strange illness afflicted 24 diplomatic staff members working at the U.S. embassy in Havana, Cuba. Employees reported symptoms such as headaches, confusion, hearing loss. They talked about hearing strange sounds, triggering speculation the Cubans were employing a new acoustic weapon to harass embassy employees. Other scientists dismissed the idea of a sonic weapon as impractical. 
 
 On September 1 science reporter William Broad jumped into this morass with a long article in The New York Times. His theory: the Cubans were employing a microwave weapon against U.S. embassy employees, causing sonic delusions and “very real brain damage”. He based his theory on the microwave auditory effect, in which pulses of microwave energy of the sort emitted by radar elicits auditory sensations in exposed individuals. 
 
 As the scientist who first proposed the now-accepted explanation of the effect in my 1974 Science article, I find the theory wildly implausible. To elicit auditory sensations, individuals must be exposed to intense but brief (microsecond) pulses of microwave energy. The pulses are sufficient to heat brain tissue by a few microdegrees in a few microseconds, and the resulting thermal expansion launches an acoustic wave in the brain that the subject perceives as sound. The acoustic pressures are many orders of magnitude too weak to cause tissue damage. They elicit audible sensations only because of the exquisite sensitivity of the human auditory system, and represent a near-threshold hearing phenomenon. To actually damage the brain, the microwaves would have to be so intense they would actually burn the subject, which has never happened in any of these incidents. 
 
 To induce such an effect, one could cobble together a device from a military radar set or a commercial microwave generator, such as the one I used in my original experiments, and then direct a beam at a distant target. But the difficulty of aiming the beam at a person’s head some distance away would be daunting. You would have to know exactly where the victim’s head is located. You could use a much higher power radar such as that used for airport traffic control and spray the beam over a wide area, but the equipment then would be very large and cumbersome. Microwave antennas could also be embedded within the embassy walls, along with some kind of aiming device, but they would be easy to detect. 
 
 But why bother with a device that produces near-threshold hearing sensations? There are simpler ways to harass people if that is the goal. Even now, a year after the incidents were reported, the facts of the matter remain unclear. A follow-up medical examination of 21 of the affected individuals by a neuroscience group led by Doug Smith at the University of Pennsylvania (my colleagues, in fact) found equivocal evidence the individuals had sustained “injury to widespread brain networks”. Neuroskeptic, a neuroscientist who blogs anonymously in Discover magazine, brutally reviewed the Penn study. The blogger and other critical scientists suggested the findings were statistical artifacts due to the many tests the Penn group employed on the subjects. Other scientists have argued psychological factors were involved instead. Taken together, the results seem too scattered to allow firm conclusions to be drawn. 
 
 In October 2017 Josh Lederman and Michael Weissenstein from the Associated Press made recordings available of the sounds that the employees reported hearing. If those indeed were the sounds, that would rule out the microwave auditory effect where the microwave-induced vibrations exist only within the head. Chen Yan, Kevin Fu and Wenyuan Xu (of Zhejiang University and the University of Michigan) showed the sounds in the AP recordings are characteristic of those produced by the interaction of two inaudible ultrasound beams via an effect known as intermodulation distortion. Ultrasound is widely used in burglar detectors, room occupancy sensors and other increasingly common appliances, and some individuals report unpleasant audible sensations from such devices. Intermodulation distortion is increasingly being employed to jam microphones used to record concert music illegally or for eavesdropping. Yan and colleagues report ultrasound can be used for eavesdropping purposes as well, by picking up vibrations in objects produced by human speech. 
 
 In short, it is reasonable to guess the sounds were inadvertently produced by ultrasound devices, possibly even spy tech, but without malicious intent against the embassy personnel. The incidents occurred about the time of the 2016 U.S. election, and the Cubans undoubtedly were desperate for intelligence about U.S. intentions. 
 
 There is even a historical parallel to the recent incidents: In 1972 it became publicly known the Soviets had been irradiating the U.S. embassy in Moscow with low-level microwave energy from the 1950s through the 1970s. Neither side disclosed the reason for this. (A reasonable guess is the Russians were trying to disrupt U.S. listening equipment or to collect data from their own bugs in the building.) The media published hyperbolic stories about supposed attempts to harm the embassy staff, fueling a generation of speculation about microwave “neurowarfare.” 
 
 We don’t know all the facts about the earlier incidents or the current ones, and no government is likely to provide them. Much of the information available is distinctly anecdotal. The Times story is not “fake news” but the real facts of the matter may be quite different from those presented by its distinguished journalist. ||||| Havana (CNN) A Cuban government investigator looking into reports of mysterious acoustic attacks on US and Canadian diplomats on the communist-run island on Monday dismissed a US government theory that microwave weapons emitting concentrated beams of radiation may have been used in the incidents. 
 
 "If you look at the alleged events, there have been reports that there are several people in a room with thick walls and thick windows and only one person was targeted. This is a kind of weapon that doesn't exist," said Dr. Mitchell Valdes-Sosa, a well-known neurologist who is part of the Cuban special task force investigating the alleged attacks. "It's science fiction, not science," he said. 
 
 "First, it was sonic weapons, now microwave. What's next, kryptonite?" the investigator said in an interview with CNN at his research center in Havana, referring to an earlier theory that sonic weapons emitting high-powered ultrasound waves could have caused the injuries. 
 
 Valdes-Sosa said researchers and investigators are working on a paper to rebut the microwave weapons theory. 
 
 Previously, the government not only denied involvement in the attacks but cast doubt on whether they actually occurred. In June, Cuba's Foreign Ministry said "political motivations" drove the United States to withdraw its embassy personnel. 
 
 Though a March report based on the examinations of 21 diplomats who served in Cuba didn't link the attacks to microwaves, the study's lead author, Douglas Smith, director of the University of Pennsylvania's Center for Brain Injury and Repair, told The New York Times that US diplomats in Cuba and China likely suffered brain injuries and that microwaves are considered the culprit. 
 
 Valdes-Sosa said for a microwave weapon to work it would have to been used at a close distance, and none of the diplomats reported seeing the alleged perpetrators. He said that Cuban authorities had investigated the report that one diplomat who suffered an apparent attack had seen a van speed off and that the vehicle belonged to a church. 
 
 While the US has not directly blamed the Cuban government for carrying out the attacks, US officials said Cuba is responsible for safeguarding the diplomats well-being and that Cuban officials would likely know if a third government were responsible. 
 
 But Valdes-Sosa said after more than a year of US, Canadian and Cuban investigations there was still no hard proof that any attacks actually took place. 
 
 "For an attack to have occurred you have to have a real victim. First the thing we are not sure is if all these people evacuated from Cuba are really ill or have suffered do something that happened to them," Valdes-Sosa said. "Second, you have to have a perpetrator. Who would be interested? You have to have the opportunity." 
 
 In a Sunday interview with CNN, Smith said microwaves are "a main suspect" in causing the diplomats' injuries, but ultrasound and infrasound were being studied as potential causes as well. 
 
 JUST WATCHED State Department pulls employees out of Cuba Replay More Videos ... MUST WATCH State Department pulls employees out of Cuba 02:34 
 
 "It's almost like a concussion, but without a concussion -- meaning that they look like individuals who have persistent concussion symptoms but have no history of head impact," Smith said, describing the injuries and explaining that learning the cause is vital to determining the best means of preventing it. 
 
 "Just like we have ways to prevent people from having a concussion, you could think of maybe protecting your brain from these energy sources," he said. 
 
 Most of the attacks came in 2016 and 2017, though there have been a handful of reported incidents this year as well. 
 
 A senior administration official told CNN that investigators have torn apart buildings where diplomatic employees encountered the sounds but found no acoustic devices, leading law enforcement to believe that the injuries were the result of microwaves beamed from a nearby location and that the "sounds" were merely a means of masking the microwave attacks. 
 
 This is only a theory, the official said, and there is no concrete evidence to back it. However, brain scans on the injured personnel showed changes that indicate damage, the official said. 
 
 JUST WATCHED Trump: Cuba 'responsible' for diplomat attacks Replay More Videos ... MUST WATCH Trump: Cuba 'responsible' for diplomat attacks 00:18 
 
 In a statement, the US State Department on Sunday neither confirmed nor denied the possibility that microwaves were behind the diplomatic injuries. 
 
 "The health and well-being of our personnel remains our top priority," the statement said. "The investigation into the origin of these symptoms continues. The inter-agency community is working diligently to determine the cause of the symptoms, as well as to develop mitigation strategies." 
 
 Secretary of State Mike Pompeo said earlier this year he was establishing a Health Incidents Response Task Force , led by Deputy Secretary of State John Sullivan and including representatives from the departments of Justice as well as Health and Human Services. 
 
 The task force will serve as the "coordinating body for department and interagency activities, including identification and treatment of affected personnel and family members, investigation and risk mitigation, messaging, and diplomatic outreach," Pompeo said in a statement. 
 
 The sophistication of the attack has led US officials to suspect a third country is involved, perhaps as retribution against the United States or Canada -- whose diplomats have also been targeted -- or to drive a wedge between those countries and Cuba. 
 
 In August 2017, officials included Russia among a list of countries that have an adversarial relationship with the United States and that American investigators suspected might be involved. ||||| Eight Canadians posted to Cuba have experienced mysterious symptoms such as headaches, dizziness and nose bleeds in recent months, but Global Affairs officials say they are still at a loss to explain what is causing them. 
 
 The most recent incident affecting Canadian diplomats and members of their families took place in December. The person affected said they suddenly felt a wave of pressure. Symptoms reported by others have included headaches, dizziness, nose bleeds, loss of balance and sleeplessness. The symptoms reported by the Canadians have not been as severe as those reported by some Americans. 
 
 While one person affected continues to experience headaches, Canadian officials said Wednesday there is no indication following medical testing that anyone has experienced permanent damage. 
 
 Officials told reporters during a background briefing in Ottawa Wednesday they are in uncharted territory and have never seen anything like it anywhere else in the world. At this point, they said, they haven't ruled out anything, including foul play. 
 
 The mysterious ailments, which have triggered speculation worthy of a spy thriller, appear to only be hitting Canadian and American diplomats posted to Havana, Cuba. 
 
 U.S. media reported last year that U.S. authorities were investigating the possibility the diplomats and their families had been targeted by some kind of "sonic attack." However, The Associated Press on Monday cited a new FBI report that said the U.S. has found no evidence sonic waves were used. 
 
 U.S. officials told a congressional hearing Tuesday they are still working on several theories — including the possibility a virus was used. 
 
 Canadian officials said there have been no reports of similar symptoms among staff of other embassies or among Cubans. Nor have there been any reports of unusual symptoms among the thousands of Canadian tourists who visit Cuba every year. 
 
 The United States reduced the number of people posted to its embassy in response to the problems reported by 24 U.S. personnel and members of their families. 
 
 However, Canadian officials said they have no plans to reduce staff at its embassy. While a small number of diplomats and their families have opted to return to Canada, others have been sent to replace them after being fully briefed. 
 
 At the same time, the government has increased security measures around both the embassy and the residences of staff members. 
 
 Among the aspects officials have been studying are infrasound, ultrasound and environmental factors. While doctors have determined that some of the symptoms could be produced by auditory trauma, they said there is no known sonic weapon. 
 
 The U.S. government warns travellers to Cuba that embassy employees have been targeted by attacks and U.S citizens could be as well — particularly around the Hotel Nacional and Hotel Capri in Havana. The Canadian government is not planning to add a similar warning to its travel advisory. 
 
 While the officials did not say it, adding a warning to a travel advisory can have significant repercussions for businesses like insurance companies and airlines. 
 
 The first reported symptoms occurred in March 2017 but there was a cluster around May 2017 after the Canadian Embassy was approached by the American Embassy and it began to ask staff if they had experienced anything. 
 
 Overall, 27 staff members or their family members went through a medical examination and eight received further followup medical treatment. 
 
 The government is also doing baseline testing of those being posted to the embassy in Cuba, including those sent there temporarily, to allow them to determine if there are any future changes. 
 
 While a number of American staff said they heard a high-pitched sound before they began experiencing symptoms, only one Canadian reported that kind of sound. 
 
 The Canadians reported feeling the symptoms at their homes, rather than at the embassy. 
 
 Officials said Cuban officials appear to be as puzzled by the strange symptoms as the Canadians and Americans.
– Microwave weapons? That's the latest theory being floated to explain the mysterious ailments suffered by staffers at the American embassy in Cuba. But now a pioneering scientist in that field thinks the idea—based on a principle called the microwave auditory effect—is bogus. Kenneth Foster is a professor of bioengineering at Penn who explained the auditory effect in a 1974 study. At Scientific American, he assesses what's known about the Cuban ailments and lays out why it's "wildly implausible" that microwaves are to blame. For one thing, any such weapon powerful enough to cause brain damage would almost certainly burn the victims, too, and that didn't happen. Instead, Foster suggests that a much simpler explanation is likely. "It is reasonable to guess the sounds were inadvertently produced by ultrasound devices, possibly even spytech, but without malicious intent against the embassy personnel," he writes. Foster cites this earlier investigation from the AP revealing the sounds that the victims are believed to have heard, and he says the sounds are consistent with ultrasound devices interacting with each other. It makes sense to him that the Cubans might have been trying to listen in on Americans with these relatively common gizmos. "The incidents occurred about the time of the 2016 US election, and the Cubans undoubtedly were desperate for intelligence about US intentions." A Cuban scientist, meanwhile, agrees that the microwave theory is far-fetched. "First, it was sonic weapons, now microwave," he told CNN. "What's next, kryptonite?"