Have you ever had unexplained fatigue, dizziness and a painful buzzing sound in your ears?
Well, if you're a US spy, diplomat, military personnel or Government official, you could be experiencing Havana Syndrome.
The cause of the syndrome is unknown, with the first reported case happening to personnel stationed in Cuba in 2016.
But since the first complaint emerged, reports of the mystery illness are now in the hundreds and span the entire globe – leaving a real impact on the US' ability to operate abroad.
The US has struggled to find hard evidence tying Havana Syndrome down – some think it is a weapon, others think it is all in the mind.
One theory has honed in on microwaves as the most likely reason for the illness.
There was speculation after the first cases that either the Cuban Government or a hard-line faction against the improving US-Cuba relations may have targeted the US personnel with a sonic weapon.
However, once cases began cropping up around the world, this theory fell flat.
And, as recently as yesterday, 13 October, there were reports of possible cases in Colombia – just days after US President Joe Biden vowed to find "the cause and who is responsible".
An estimated 200 US officials have been affected by Havana Syndrome, with some left with symptoms for months.
More than half of those who have reported the mystery illness were reportedly CIA employees.
And another possibility has since come into the picture – one rooted in the espionage and secretive nature of the Cold War.
A professor from the US immediately thought microwaves were responsible for the mysterious sounds in Havana.
Decades earlier, he'd heard the sounds himself.
People had reported, since its emergence in the Second World War, they could hear something when a nearby radar was turned on – even though there was no external noise.
Dr Allen Frey later made the case that the noises were caused by microwaves interacting with the nervous system – but the causes and implications remained unclear.
But, with science the focus of superpower rivalry during the Cold War, microwaves were explored.
And a group of Americans in Moscow were worried they were being zapped with microwaves – and that the US government had covered it up.
They were right, and for almost 25 years, the US embassy in Moscow was bathed in a wide, invisible, low-level beam of microwaves, with those inside none the wiser.
It wasn't until 1974, when new ambassador Walter Stoessel arrived, that everyone was told.
After threatening to resign unless everyone in the building was told, the secret was out and the staff were informed.
Watch: What was it like living in Cold War East Germany?
Later, Ambassador Stoessel himself fell ill, with bleeding from the eyes one of his symptoms.
Now declassified, then-US Secretary of State Henry Kissinger linked Stoessel's illness to microwaves and said the US was "trying to keep the thing quiet".
In 1976, screens were installed to protect people, but staff were angry and many accused the State Department of first keeping quiet and then refusing to acknowledge and health impacts.
This claim was echoed following the first cases of Havana Syndrome.
After the first case in 2016, there was a lull in reports of the illness.
In December 2017, a senior CIA officer reported a case in Russia and was later forced to retire due to the illness.
In early 2018, other cases were reported, including at the consulate in Guangzhou.
Watch: New research claims to have partially solved mystery of 'Gulf War Syndrome'.
Some of the families got in touch with Professor Beatrice Golomb, a professor at the University of California, San Diego, who had long researched the health effects of microwaves.
She said high levels of radiation were recorded by family members of personnel in China – using equipment they could purchase.
She said the "needle went off the top of the available readings".
But, after writing to the US State Department's medical team in January 2018, explaining the theory that microwaves were responsible, she was given the rather uncommitted response that her research "makes for interesting reading".
A number of problems influenced the early investigations, with the lack of consistent data and a lack of communication between the State Department and the CIA.
There have also been reported cases in Poland, Georgia and Taiwan.
Since the first case was reported, some US officials say little is known about the illness.
But others disagree, arguing the evidence for microwaves being responsible holds more weight now.
The debate is complex, but the mystery and fear of the illness remains.