Three US diplomats in Switzerland and one in Paris are said to be suffering from the mysterious ‘Havana Syndrome’, which is said to have affected more than 200 State Department employees in US embassies all over the world.

The three US diplomats are based in Geneva and the fourth one is based in the French capital Paris. None of them have been named.

‘Havana Syndrome’ is a term that has been used to depict a mysterious group of symptoms, which people, primarily US diplomats, have experienced over the last five years. Some people reportedly experience dizziness, fatigue and tinnitus for months.

Secretary of State Antony Blinken has said that the American authorities were working to get to the bottom of the mystery.

‘Havana syndrome’ first appeared in Cuba in 2016 and has affected US diplomats, intelligence officers and family members.

It is currently unclear what is causing the symptoms, but one theory is that a foreign power may be using a super weapon against the US. This theory has been dismissed by Moscow, who said that the idea that it had used a form of militarised microwaves against US representatives abroad was a “fanciful hypothesis”.

Another theory being investigated is the idea that those who have become sick with ‘Havana Syndrome’ are suffering from a mass psychogenic illness triggered by stressful situations.

The US Department of State has called these events “unexplained health incidents”, while CIA director William Burns has publicly labelled them attacks.

The investigation is ongoing.