Microwave weapons that could cause Havana Syndrome exist, experts say

Russia and possibly China have developed technology capable of injuring brain and a US company made a prototype in 2004

Portable microwave weapons capable of causing the mysterious spate of Havana Syndrome" brain injuries in US diplomats and spies have been developed by several countries in recent years, according to leading American experts in the field.

A US company also made the prototype of such a weapon for the marine corps in 2004. The weapon, codenamed Medusa, was intended to be small enough to fit in a car, and cause a temporarily incapacitating effect" but with a low probability of fatality or permanent injury".