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The Central Intelligence Agency was forced to evacuate an intelligence officer serving in Serbia after the officer suffered serious injuries consistent with those associated with Havana Syndrome, part of a rise of such attacks on U.S. officials overseas.
"We take each report we receive extremely seriously and are working to ensure that affected employees get the care and support they need," a State Department spokesman said of continued attacks on American officials.
The most recent incident in Serbia is part of what officials have called an expansion of similar attacks on U.S. spies and diplomats stationed in overseas locations. Who is perpetrating the attacks remains a mystery, though government officials and scientists believe the assailants are using what they described as a "directed-energy source."
The attacks have happened at multiple locations overseas and in the U.S. and have become more common.
Dr. James Giordano, a Georgetown University professor of neurology and adviser to the government, said in "the past 60 to 90 days, there have been a number of other reported cases" on U.S. soil and around the world.
"They are seen as valid reports with verified health indicators," Giordano said.
The attacks can cause symptoms such as dizziness, memory loss and a range of other issues, resulting in a drop in morale within the State Department and the CIA and causing some officials to be reluctant to take overseas assignments.
Some attacks have even targeted top officials within the Biden administration, most recently when members of CIA Director William Burns' staff reported symptoms consistent with an attack during a trip to India earlier this month.
Most frustrating is that the U.S. government still doesn't know who is behind the attacks or have certainty about how they're being carried out.
"In terms of have we gotten closer? I think the answer is yes – but not close enough to make the analytic judgment that people are waiting for," CIA Deputy Director David Cohen said earlier this month of the effort to get to the bottom of the mystery.
How to respond to the attacks if they are coming from a foreign adversary such as China or Russia is also unclear, with some current and former officials believing Russia could be behind them. Russia has denied it, and no evidence has so far emerged of Russian involvement.
But Jason Killmeyer, a counterterrorism and foreign policy expert formerly with Deloitte Consulting LLP, believes the U.S. should do more even without attribution, calling for increased defensive measures and applying pressure to foreign intelligence agencies to see how they react.
"We’re five years into this thing," Killmeyer said. "There’s no ‘smoking gun’ coming."