The 2020 National Academies study found that it was unlikely that "acute high-level exposure to OPs and/or pyrethroids contributed" to the illnesses, due to a lack of evidence of exposures to those pesticides or clinical histories consistent with such exposure. However, the National Academies study committee "could not rule out the possibility, although slight, that exposure to insecticides, particularly OPs, increased susceptibility to the triggering factor(s) that caused the Embassy personnel cases." The National Academies study committee also found it "highly unlikely" that an infectious disease (such as Zika virus, which was an epidemic in Cuba in 2016–17) caused the illnesses.
In 2017, Donald Trump accused Cuba of perpetrating unspecified attacks causing these symptoms. The U.S. reduced staff at their embassy to a minimum in response. In 2018, U.S. diplomats in China reported problems similar to those reported in Cuba, as did undercover CIA agents working in other countries with partner agencies to counter Russian covert operations.
In March 2018, MRI scans and other tests taken by a chief neurologist in Pittsburgh, on an unspecified number of Canadian diplomats showed evidence of brain damage that mirrored the injuries some of their American counterparts had faced. In early 2018, Global Affairs Canada ended family postings to Cuba and withdrew all staff with families. Several of the Canadians who were impacted in 2017 were reported to still be unable to resume their work due to the severity of their ailments. The fact that, as of February 2019 , there was no knowledge of the cause of “Havana syndrome” had made it challenging for the RCMP to investigate.
In August 2017, reports began surfacing that American and Canadian diplomatic personnel in Cuba had experienced unusual, unexplained health problems dating back to late 2016. The number of American citizens experiencing symptoms was 26 as of June 2018.
In August 2017, the United States expelled two Cuban diplomats in response to the illnesses. In September, the U.S. State Department stated that it was removing non-essential staff from the US embassy, and warned U.S. citizens not to travel to Cuba. In October 2017, U.S. president Donald Trump said that "I do believe Cuba's responsible. I do believe that", going on to say "And it's a very unusual attack, as you know. But I do believe Cuba is responsible."
In early 2018, accusations similar to those reported by diplomats in Cuba began to be made by U.S. diplomats in China. The first incident reported by an American diplomat in China was in April 2018 at the Guangzhou consulate, the largest U.S. consulate in China. The employee reported that he had been experiencing symptoms since late 2017. Several individuals were taken to the United States for medical examination. Another incident had previously been reported by a USAID employee at the U.S. Embassy in Tashkent, Uzbekistan, in September 2017; the employee's report was discounted by the U.S. State Department.
An U.S. Office of Special Counsel investigation resulted in an April 2020 determination that there was "a substantial likelihood of wrongdoing" by State Department leadership. Mark Lenzi, who was a State Department diplomatic security officer stationed in Guangzhou, accused the department of a "deliberate, high-level cover-up" and of failing to protect their employees. Marc Polymeropoulos, a 26-year CIA veteran, who retired in 2019, similarly felt betrayed by CIA leadership, accusing the agency of failing to respond appropriately to a vertigo-inducing attack in Moscow in December 2017 (which Polymeropoulos called "the most terrifying experience of my life" and more frightening than experiences in Iraq and Afghanistan). Polymeropoulos fought with the CIA for years to obtain specialized medical treatment, after the agency cast doubt on the similarities between the symptoms he experienced and those suffered by the diplomats in Havana. Polymeropoulos was ultimately diagnosed at the U.S. government's Walter Reed Medical Center with traumatic brain injury; attorney Mark Zaid, who represented almost a dozen clients who had become ill from similar attacks, said that Polymeropoulos was the only one of his clients who had received treatment at Walter Reed, with others obtaining treatment only from personal doctors or academic medical centers.
In response to a December 2017 request from the State Department, the Centers for Disease Control and Prevention conducted a "Cuba Unexplained Events Investigation." The two-year investigation of the medical records of 95 U.S. diplomats and family members in Havana who reported symptoms, resulted in a final report, marked for official use only, dated December 2019. In January 2021, the report was obtained by both BuzzFeed News and George Washington University's National Security Archive pursuant to the Freedom of Information Act requests (some material in the released report was redacted for medical privacy reasons). The CDC developed a "case definition" of the Havana syndrome, consisting of a biphasic (two-stage) syndrome, with a first phase of symptoms (sometimes closely after an auditory or sensory event) followed by a subsequent onset of "cognitive deficits or vestibular disturbances" some time later. The report concluded that, "Of the 95 persons whose medical records CDC evaluated, 15 had illnesses that met the criteria for a presumptive case definition. CDC classified 31 others as possible cases and the remaining 49 as not likely to be a case." Two years later, six of the subjects in the CDC investigation were still being rehabilitated for their injuries, and four of them were still unable to return to work. The CDC decided not to conduct a retrospective case–control study because of the length of time between the event and the onset of symptoms, which could lead to recall and selection biases that "could generate misleading or obscured findings." The CDC concluded, "The evaluations conducted thus far have not identified a mechanism of injury, process of exposure, effective treatment, or mitigating factor for the unexplained cluster of symptoms experienced by those stationed in Havana."
Subsequent studies of the affected diplomats in Cuba, published in the journal JAMA in 2018, found evidence that the diplomats experienced some form of brain injury, but did not determine the cause of the injuries. While there is no expert consensus on the cause of the symptoms, a co-author of the JAMA study considered microwave weapons to be "a main suspect" for the phenomenon. U.S. National Academies of Sciences, Engineering, and Medicine expert committee concluded in December 2020 that microwave energy (specifically, directed pulsed RF energy) "appears to be the most plausible mechanism in explaining these cases among those that the committee considered" but that "each possible cause remains speculative." The U.S. intelligence services have not reached a consensus or formal determination on the cause of the Havana syndrome, but unnamed sources in intelligence and two presidential administrations have expressed suspicions to the press that Russian military intelligence is responsible.
In January 2018, at the direction of Secretary of State Rex Tillerson, the Department of State convened an Accountability Review Board, which is "an internal State Department mechanism to review security incidents involving diplomatic personnel." Retired United States Ambassador to Libya Peter Bodde was chosen to lead the board.
In January 2018, the Associated Press reported that a non-public FBI report found no evidence of an intentional sonic attack. A November 2018 report in the New Yorker found that the FBI's investigation into the incidents was stymied by conflict with the CIA and the State Department; the CIA was reluctant to reveal, even to other U.S. government agencies, the identities of affected officers, because of the CIA's concern about possible leaks. Federal rules on the privacy of employee medical records also hindered the investigation.
At the request of the U.S. government, University of Pennsylvania researchers examined 21 affected diplomats, and the preliminary results were published in the Journal of the American Medical Association (JAMA) in March 2018. The report "found no evidence of white matter tract abnormalities" in affected diplomats, beyond what might be seen in a control group of the same age, and described "a new syndrome in the diplomats that resembles persistent concussion." While some of those affected recovered swiftly, others had symptoms lasting for months. The study concluded that "the diplomats appear to have sustained injury to widespread brain networks." Some experts criticized the study, arguing that there was "no proof that any kind of energy source affected the diplomats, or even that an attack took place." Subsequent study findings by the University of Pennsylvania team, published in July 2019, found that compared to a healthy control group, the diplomats who had reported injury had experienced brain trauma; advanced MRI scans (specifically res-fMRI, multimodal MRI, and diffusion MRI) revealed "differences in whole brain white matter volume, regional gray and white matter volume, cerebellar microstructural integrity, and functional connectivity in the auditory and visuospatial subnetworks" but found no differences in executive functions. The study concluded that the U.S. government personnel had been physically injured in a way consistent with the symptoms that they described, but expressed no conclusion on the cause or source of the injury. The New York Times reported: "Outside experts were divided on the study's conclusions. Some saw important new evidence; others say it is merely a first step toward an explanation, and difficult to interpret given the small number of patients."
In March 2018, Kevin Fu and a team of computer scientists at the University of Michigan reported in a study that ultrasound—specifically, intermodulation distortion from multiple inaudible ultrasonic signals—from malfunctioning or improperly placed Cuban surveillance equipment could have been the origin of the reported sounds.
On March 2, 2018, the U.S. State Department announced it would continue to staff its embassy in Havana at the minimum level required to perform "core diplomatic and consular functions" due to concerns about health attacks on staff. The embassy had been operating under "ordered departure status" since September, but the status was set to expire. This announcement served to extend the staff reductions indefinitely.
Answering questions from the House Foreign Affairs Committee on May 23, 2018, Secretary of State Mike Pompeo testified that U.S. diplomatic staff in Guangzhou had reported symptoms "very similar" to, and "entirely consistent" with, those reported from Cuba. On June 6, 2018, The New York Times reported that at least two additional U.S. diplomats stationed at the Guangzhou consulate had been evacuated from China, and reported that "it remains unclear whether the illnesses are the result of attacks at all. Other theories have included toxins, listening devices that accidentally emitted harmful sounds, or even mass hysteria." In June 2018, the State Department announced that a task force had been assembled to investigate the reports and expanded their health warning to all of mainland China amid reports some US diplomats outside of Guangzhou had experienced the same symptoms resembling a brain injury. The warning told anyone who experienced "unusual acute auditory or sensory phenomena accompanied by unusual sounds or piercing noises" to "not attempt to locate their source."
In 2019, the government of Canada announced that it was reducing its embassy staff in Havana after a 14th Canadian diplomat reported symptoms of Havana syndrome in late December 2018. In February 2019, several Canadian diplomats sued the Canadian government, arguing that it failed to protect them or promptly address serious health concerns. The government has sought to dismiss the suit, arguing in November 2019 that it was not negligent and did not breach its duties to its employees. In court filings, the government acknowledged that several of the 14 plaintiffs in the suit suffered from concussion-like symptoms, but said that no definitive cause or medical diagnosis had been ascertained. In a November 2019 statement, Global Affairs Canada said, "We continue to investigate the potential causes of the unusual health symptoms."
In 2019, a White House official reported experiencing debilitating symptoms while walking her dog in a Virginia suburb of Washington; the incident was publicly reported in 2020. In November 2020, a similar incident was reported on The Ellipse, a lawn adjacent to the south side of the White House. Both incidents were similar to those that were reported to have struck dozens of U.S. personnel overseas, including CIA and State Department personnel. Federal agencies investigated the incident at The Ellipse, and Defense Department officials briefed members of the Senate Armed Services Committee and House Armed Services Committee in April 2021. Investigators told members of Congress that they had not been able to determine the cause of the events or who was responsible, although officials indicated that it was possible that Russia or China were responsible.
Roughly 130 total possible cases of attacks have been reported, with about 50 affecting CIA personnel, and the rest being primarily U.S. military personnel, State Department personnel, and their family members. Attacks targeting U.S. intelligence personnel were reported, beginning in late 2017, in locations around the world, including in Moscow, Russia; Poland; Tbilisi, Georgia; Taiwan and Australia; other reports came from Colombia, Kyrgyzstan, Uzbekistan, and Austria, among other countries. A 2021 article by Julia Ioffe, published in GQ magazine, stated that the "most compelling evidence" of Russian involvement derives from mobile phone tracking: "Using this sort of data, CIA investigators were able to deduce the whereabouts of Russian agents, and place them in close physical proximity to the CIA officers at the time they had been attacked when they were in Poland, Georgia, Australia, and Taiwan. In each case, individuals believed to be FSB agents were within range of the CIA officers who had been hit in 2019. In two of the incidents, location data apparently showed FSB agents in the same hotel at the same time their targets experienced the onset of symptoms."
U.S. personnel in Cuba made sound recordings which they released to the Associated Press. In January 2019, biologists Alexander L. Stubbs of the University of California, Berkeley and Fernando Montealegre-Z of the University of Lincoln analyzed these recordings and concluded that the sound was caused by the calling song of the Indies short-tailed cricket (Anurogryllus celerinictus) rather than a technological device. Stubbs and Montealegre-Z matched the song's "pulse repetition rate, power spectrum, pulse rate stability, and oscillations per pulse" to the recording. Stubbs and Montealegre wrote that "Although the causes of the health problems reported by embassy personnel are beyond the scope of this paper and called for "more rigorous research into the source of these ailments, including the potential psychogenic effects, as well as possible physiological explanations unrelated to sonic attacks." This conclusion was comparable to a 2017 hypothesis from Cuban scientists that the sound on the same recording is from Jamaican field crickets. Reuters reported that JASON, a group of physicists and scientists who advise the U.S. government, determined that "a rare jungle cricket" was the cause of the sounds in Havana.
A 2019 study commissioned by Global Affairs Canada of 23 exposed Canadian diplomats, completed in May 2019, found "clinical, imaging, and biochemical evidence consistent with the hypothesis" that over-exposure to cholinesterase inhibitors (a class of neurotoxic pesticide) such as pyrethroids and organophosphates (OPs) as a cause of brain injury; the embassies and other places in Cuba had been sprayed frequently as an anti-Zika virus mosquito control measure. The study concluded that other possible causes could not be ruled out.
A 2021 report in the New Yorker cited a number of incidents recounted by Mark Vandroff, who served as the senior director for defense policy at the National Security Council: "One of the most dramatic episodes involved a U.S. military officer stationed in a country with a large Russian presence. As the officer pulled his car into a busy intersection, he suddenly felt as though his head were going to explode. His two-year-old son, in a car seat in the back, started screaming. As the officer sped out of the intersection, the pressure in his head ceased, and his son went quiet. A remarkably similar incident was reported by a C.I.A. officer who was stationed in the same city, and who had no connection to the military officer." Three White House staffers reported symptoms at the InterContinental London Park Lane in late May 2019. One of the CIA officials who suffered symptoms in Australia and Taiwan was one of the top five-ranking officials in the agency. The Russian embassy in Australia dismissed reports of Russian operatives targeting CIA personnel in Australia.
In October 2020, the New York Times reported that U.S. diplomats and intelligence officers, including senior leaders, had clashed with Trump administration appointees, including CIA director Gina Haspel and State Department leaders, over the nature and causes of the suspected attacks. A Times investigation found that the State Department had "produced inconsistent assessments of patients and events, ignored outside medical diagnoses and withheld basic information from Congress." Despite the general view within the U.S. government that Russia was responsible, two U.S. officials told the Times that Haspel was not convinced of Russia's responsibility, or even whether an attack occurred.
In December 2020, a study by an expert committee of the U.S. National Academies of Sciences, Engineering, and Medicine, commissioned by the State Department, released its report, concluding that "Overall, directed pulsed RF energy ... appears to be the most plausible mechanism in explaining these cases among those that the committee considered" but that "each possible cause remains speculative" and that "the report should not be viewed as conclusive". Chaired by David Relman, the committee included Linda Birnbaum, Ronald Brookmeyer, Caroline Buckee, Joseph Fins, David A. Whelan, and others. The panel stated that a lack of information (such as medical testing data about affected persons) limited what it could conclude about the plausible explanations for the phenomenon.
In December 2020, the CIA established a task force to investigate the attacks. The agency set up the task force after continued reports of debilitating attacks against CIA officers in various places around the world. The CIA expanded its investigation under Director William Joseph Burns, who took office in 2021. In March 2021, the State Department appointed a senior official to oversee the department's response to the attacks.
Near the end of the Trump administration, the Defense Department established a task force to investigate reports of attacks on DoD personnel abroad. The DoD established the task force partly due to frustration over what DoD officials considered to be a sluggish and lackluster response by the CIA and Department of State. Christopher C. Miller, who was acting defense secretary at the time, said in 2021 that, "I knew CIA and Department of State were not taking this shit seriously and we wanted to shame them into it by establishing our task force." Miller said that he began to consider the reports of mysterious symptoms to be a high priority in December 2020, after he conducted an interview with a person with major combat experience who detailed symptoms.
A 2018 State Department report was declassified, and posted on the George Washington University's National Security Archive, after Freedom of Information Act litigation brought by the James Madison Project. The documents indicate that the initial State Department handling of the attacks was botched. Peter Kornbluh of the National Security Archive noted that the 2018 report concluded that the department's "initial investigation assessment of what was going on" was marred by chaos, disorganization, and excessive secrecy. In 2021, sources familiar with the various ongoing investigations told CNN that a primary obstacle to progress by the U.S. government in investigating the syndrome was a lack of interagency coordination between the CIA, FBI, Centers for Disease Control and Prevention, and State Department, which conducted separate and "largely siloed" investigations. The limited coordination among the varying agencies was based in part of "the highly classified nature of some details and the privacy restrictions of health records, and that has hampered progress."
The Senate Intelligence Committee leadership (chairman Mark Warner and vice chairman Marco Rubio) said in 2021 that it was working with Burns and the CIA on connection with the investigation, saying "We have already held fact finding hearings on these debilitating attacks, many of which result in medically confirmed cases of Traumatic Brain Injury, and will do more." In May 2021, Politico reported that intelligence officials had recently told Congress that they had 'intensified their investigation ... to include all 18 federal intelligence agencies and that the investigation was focused on the potential involvement of GRU, the Russian spy agency.
The U.S. State Department said in February 2021 that its ongoing investigation was "a high priority" for the department. Citing unnamed intelligence and government officials, The New York Times reported in July 2021 that that National Security Council, Central Intelligence Agency, and Director of National Intelligence established two outside panels, one to investigate potential causes and the other to develop defensive countermeasures for personnel protection; cleared external scientists will be permitted to view relevant classified intelligence in their investigations.
In a March 2021 article published in Science-Based Medicine, bioengineer Kenneth Foster and biophysicist CK Chou criticized the National Academies study; they argued that the symptoms were not cause by microwave weapons, that the committee was "steered by its agenda to focus on microwave weapons as the cause of the symptoms" and "lacked the time and resources to explore other theories," such as participation by a social psychologist with expertise in mass psychogenic illness."
In May 2021, Politico reported that three current and former U.S. officials "with direct knowledge of the discussions" said that the U.S. government suspected that Russia's GRU, the Russian military intelligence agency, was behind alleged attacks, although the U.S. Intelligence Community have not "reached a consensus or made a formal determination." In May 2021, New Yorker reported that the U.S. government's "working hypothesis" was that GRU agents "have been aiming microwave-radiation devices at U.S. officials to collect intelligence from their computers and cell phones, and that these devices can cause serious harm to the people they target." The U.S. government has not publicly accused Russia of the attacks; U.S. intelligence officials privately refer to the events as "attacks" but publicly referred to them as "anomalous health incidents." According to two officials interviewed by Politico, "While investigators have not determined definitively that these incidents are caused by a specific weapon, some believe any such device would be primarily transported by vehicle" and that "Some could be small enough to fit into a large backpack, and an individual can be targeted from 500 to 1,000 yards away." James Lin of the University of Illinois, an expert on the biological effects of microwave energy, agreed that an Havana syndrome attack could be caused by a small apparatus that could fit in a van or SUV.
In response to the Havana Syndrome, ten US Senators proposed a Senate bill that would close a loophole in the Federal Employees' Compensation Act which would normally not cover damage to organs such as the brain and heart. The Helping American Victims Afflicted by Neurological Attacks (HAVANA) Act, authorizes the CIA Director and the Secretary of State to provide financial support for personnel suffering brain injuries. The bipartisan bill unanimously passed the Senate in June 2021.
In July 2021, the State Department confirmed it was investigating upwards of 20 cases of Havana syndrome-like symptoms in officials stationed in Vienna. The Austrian foreign ministry stated it was collaborating with American investigators. Aside from Havana itself, Vienna is the city reporting the most incidents. While no suspects have been named for the Vienna cases, it has been noted that Vienna is currently hosting indirect talks between the United States and Iran on reviving the 2015 Iran deal.