In late 2016, intelligence officers at the newly reopened U.S. embassy in Havana began reporting a strange sequence: a sudden, localized sound or a feeling of pressure, usually at night in their homes, followed by headaches, dizziness, ringing in the ears and trouble concentrating. Over the next five years similar reports came from Guangzhou, Moscow, Vienna, Berlin, Tbilisi, Hanoi, Bogotá, New Delhi and Washington itself. The government calls them anomalous health incidents. The public calls them Havana Syndrome.

Ten years on, three records sit side by side and do not agree. The medical record says the symptoms are real and often disabling, but that brain scans show no injury. The scientific record says pulsed radio-frequency energy is the most plausible external cause, but no device has ever been tied to an incident. The intelligence record is formally split: five agencies say foreign involvement is very unlikely, two dissent, and a House subcommittee says the majority finding was engineered.

Two things changed in 2026. The Pentagon has spent more than a year testing a pulsed radio-frequency device that the government bought covertly for an eight-figure sum, and in July it renamed its task force the Directed Energy Bio-Effects team and issued its first compensation payments. Meanwhile Canadian diplomats whose children fell ill in Havana are pressing Ottawa for an inquiry.