One week after the Trump administration issued a travel warning for Cuba, it said that a "handful" of Americans who traveled to the island country reported to the State Department that they "experienced symptoms similar" to those affecting nearly two dozen embassy personnel in Havana. Twenty-two American government employees have been hit by "targeted" attacks, with symptoms ranging from dizziness, to headache and fatigue, to hearing loss, to traumatic brain injury. But, if verified, the claims in the statement from the State Department would mark a dramatic escalation of the ongoing mystery that has vexed U.S. investigators and so far...