WASHINGTON - The top U.S. spy agency has concluded a mysterious illness plaguing American diplomats and other officials around the world is not nearly as widespread as initially feared and is most likely not the work of a foreign adversary.
But the Central Intelligence Agency also cautioned that a smaller number of cases continue to defy explanation, with one official warning that in those cases, "We have not ruled out the involvement of a foreign actor."
Since 2016, when it was first reported by diplomats at the U.S. Embassy in Havana, hundreds of U.S. personnel have reported getting sick, with symptoms ranging from nausea and dizziness to debilitating headaches and memory problems.
Suspected cases of so-called Havana syndrome were reported in Russia, China, Poland and Austria, and the sickness affected some U.S. officials so badly their careers derailed.
Yet an interim report Thursday by the CIA finds that most of the illnesses, also known as anomalous health incidents, or AHI, are not a mystery at all.
'We assess that the majority of the reported AHI cases can be reasonably explained by medical conditions or environmental and technical factors, including previously undiagnosed illnesses,' a CIA official told VOA on Thursday on the condition of anonymity in order to discuss the report.
The official declined to say exactly how many cases the agency investigated, describing the number as 'dynamic,' and noted that reports increased dramatically once the government encouraged workers to report any symptoms that could be connected to Havana syndrome.
Various unofficial accounts have put the number anywhere from several hundred to as many as 1,000.
However, there are 'a couple of dozen cases' for which there are still no answers, the official said.
'There is a subset of cases, including some of our toughest cases, that remain unresolved,' the official said.
The location of many of the first-reported cases - Havana, Russia and China - gave rise to speculation that Havana syndrome was not so much an illness as it was an effort to harm U.S. diplomats and intelligence personnel.
A 2020 report by the National Academy of Sciences further fueled such concerns, concluding that 'directed, pulsed radio frequency energy appears to be the most plausible mechanism in explaining' the growing number of cases.
The CIA interim report, while not ruling out that someone or something may be causing Havana syndrome in the unexplained cases, called the use of a weapon unlikely.
'We assess that it is unlikely that a foreign adversary, including Russia, is conducting a sustained worldwide campaign harming U.S. personnel with a weapon or mechanism,' the official said. 'We have so far not found evidence of state actor involvement in any incident.'
Despite the findings of the interim report, U.S. officials said Thursday that they continue to take the reports of illnesses among U.S. government employees seriously, and that making sure medical care was available remains a top priority.
'I have no higher priority as secretary than the health and safety of all of our colleagues and their families,' Secretary of State Antony Blinken told reporters Thursday during a news conference in Berlin.
'When you talk to people, when you hear them, when you hear what they've been through, there is no doubt in my mind but that they have had real experiences, real symptoms, and real suffering,' he said. 'We are going to continue to do everything we can with all the resources we can bring to bear to understand, again, what happened, why, and who might be responsible. And we are leaving no stone unturned.'
CIA Director William Burns also emphasized the need to care for those who have been ill, and for any personnel that could be affected in the future, describing their suffering as real.
'While we have reached some significant interim findings, we are not done,' Burns said in a statement. 'We will continue the mission to investigate these incidents and provide access to world-class care for those who need it.'
Some U.S. lawmakers praised the efforts of the CIA to determine the cause of the ailments but said more still needs to be done.
'Reports of anomalous health incidents among intelligence, diplomatic and military personnel emerged as early as 2016 but were not always taken seriously,' the Senate Intelligence Committee chairman, Democrat Mark Warner, said in a statement.
'I am heartened that there are now procedures in place to ensure that those who are affected by these anomalous health incidents finally have access to the world-class care that they deserve,' he said, adding, 'The Senate Intelligence Committee will continue pressing for answers.'
Republican Marco Rubio, the Senate Intelligence Committee's vice chair, was equally adamant that lawmakers would keep pressing U.S. intelligence officials for answers.
'The CIA must continue to make this issue a priority,' Rubio said, noting the possibility that the unresolved cases could still be 'the work of a foreign government or a specific weapon or device.'
U.S. lawmakers, led by Warner, Rubio and Maine Republican Senator Susan Collins, passed the Helping American Victims Afflicted by Neurological Attacks Act, or HAVANA Act, last year, when it was signed by President Joe Biden.
The law provides financial support for U.S. government employees suffering from symptoms attributed to Havana syndrome.