What you need to know about “Havana Syndrome,” the mysterious illness affecting U.S. officials stationed around the world — and whether there’s anything the United States can do about it.

“Havana Syndrome” first popped up in 2016 when a group of people at the U.S. embassy in Cuba reported a wide-ranging set of debilitating symptoms such as headache, nausea, tinnitus and memory loss.

Five years later, 200 people are known to have shown symptoms of the mysterious illness. The Washington Post broke the news that the head of the CIA station in Vienna was recently recalled for allegedly failing to take the “Havana Syndrome” seriously.

Intelligence reporter Shane Harris explains what we know about the strange syndrome, and the possible political repercussions if it is the result of a deliberate attack from a foreign adversary.

What we know about Havana Syndrome