Havana Syndrome: FBI warns staff amid reports of symptoms among agents

FBI advises employees on how to respond if they show signs of mysterious ailment which manifests as a brain injury

The FBI has warned its employees about Havana Syndrome, a mysterious ailment that appears to have affected US diplomats and spies in several countries in recent years and manifests as a brain injury.

More than 200 US officials, from the state department, CIA and national security council (NSC), have suffered from some form of symptoms - including dizziness, nausea and headaches. The phenomenon was first identified in Cuba but has happened elsewhere.