What is Havana Syndrome, the mysterious illness afflicting US diplomats from China to Vietnam?

US Vice-President Kamala Harris’ flight from Singapore to Vietnam on Tuesday took off three hours later than scheduled, after concerns about an “anomalous health incident” in Hanoi.The US State Department has frequently used that phrase to describe the so-called Havana Syndrome, a mysterious condition that has been reported by dozens of US diplomats and intelligence officials worldwide, including in China, Austria and Cuba, over the past five years.NBC News later reported that at least two US…