Patient Zero was a fit and healthy man in his 30s who was working as a CIA officer on deployment in Cuba when he turned up at one of the island's health centres on December 30 2016, complaining of dizziness and headaches.

In later accounts, he would tell officials that he felt as though a powerful, high-pitched sonic beam had been aimed directly at him in his home in Havana.

It was the first known case of what has since been dubbed 'Havana syndrome', a mystery illness which sickened more than 80 American spies, diplomats, government staff, and their families in the years after the US re-opened its embassy in Cuba in 2015, for the first time in 54 years.

Some described being plagued in their homes by bizarre clicking and grating noises which felt as though they were "coming at them", or a continual humming and buzzing that was so annoying they felt forced to turn television up full blast to try to drown it out.


For others, the impact was more debilitating.

They felt dizzy, nauseous, developed severe headaches or migraines, loss of balance, nosebleeds, tinnitus, memory impairment, fatigue, or suffered strange sensory disturbances - hearing sounds like grinding metal, or feeling as though the air inside a car was moving even with the windows closed.

In some cases, people became so impaired they had to give up work.

Since then, roughly 1000 reports of similar symptoms have emerged around the globe, including among US officials attending the last year's Nato summit in Lithuania.

A joint investigation earlier this week by CBS, Der Spiegel, and The Insider now traces the first suspected cases to Germany in 2014, and suggests that victims may have been targeted by a Russian intelligence unit using a sonic bioweapon.

One woman - an FBI agent - described feeling as though she had been hit by a powerful force at her home in Florida 2021.

The sound in her ears was "like a dentist drilling on steroids" and she ultimately passed out, going on to develop problems with memory and concentration.

Since reports of 'Havana Syndrome' first hit the news in 2017, the controversial saga has hovered uncertainly between military and medical explanations.

In 2018, an FBI probe concluded that the outbreak was most probably a mass psychogenic illness  - a kind of paranoia-induced social contagion where symptoms spread through a group without any physical or environmental cause, but because they become convinced that they are being exposed to something harmful.

In other words, the discomfort is real but the cause is psychological.

The Herald: The initial explanation laid the blame at an outbreak of mass psychogenic illnessThe initial explanation laid the blame at an outbreak of mass psychogenic illness (Image: Getty)

This was reinforced by a second classified report (eventually leaked in 2021 as a result of freedom of information requests) which found that the "mysterious sounds" reported by some staff - who at the time had been counselled to be hyperaware of any unusual noises - were in fact the mating calls of a species of cricket.

On March 18 this year, two new reports published in the prestigious Journal of the American Medical Association (JAMA) reignited the mystery once again.

The studies, carried out over five years by researchers at the National Institutes of Health (NIH), compared more than 80 US government employees and their adult family members, mostly stationed abroad and who had experienced these "anomalous health incidents" (AHIs), against a control group of age- and sex-matched healthy volunteers who had been on similar assignments without experiencing AHIs.

MRI scans detected no evidence of brain injury, nor any significant biomarker differences, that could explain the AHI group's symptoms.

The absence of structural brain damage does not necessarily prove that what occurred was a psychogenic, however.

Dr Jon Stone, a professor of neurology who specialises in Functional Neurological Disorders (FND) at Edinburgh University, said the findings did not surprise him.

FND is "something between neurology and psychiatry", he said.

Patients tend to present with neurological symptoms such as seizures, limb weakness, numbness or chronic dizziness, but brain scans will not detect any structural fault as they would for epilepsy or multiple sclerosis.

In the past, such conditions would have been stigmatised as "psychosomatic", or "hysteria", but medical science is now tracing them to "a problem with the software of the nervous system", said Prof Stone.

The Herald: There was no sign of brain injury in patients reporting 'Havana Syndrome' symptoms compared to healthy controlsThere was no sign of brain injury in patients reporting 'Havana Syndrome' symptoms compared to healthy controls (Image: PA)

Speaking to the Guardian's Science Weekly podcast in March, he said: "Usually there might be an identifiable event at the beginning which might be a minor head injury or an episode of vertigo from a viral infection, which is alarming and surprising to the person, but when that problem settles down instead of the brain adapting back to normal health the brain is stuck in a state as if the dizziness trigger is still happening."

Prof Stone noted that 24 out of the 80-plus participants in the AHI group had been diagnosed with FND, and that - like FND patients - many of those with Havana Syndrome describe symptoms getting worse over time.

He added: "We know that functional disorders are usually triggered by some unusual sensory experience and, talking to people who know about directed energy weapons, I understand that it's much easier to produce an abnormal or unpleasant sensory experience from a wouldn't cause brain damage, but it would be enough to trigger a functional disorder."

On March 31, the latest twist came as the CBS-led investigation alleged that members of a Russian military intelligence unit - known as 29155 - may have attacked the brains of US government personnel with "directed energy" weapons.


Greg Edgreen, a military investigator, told the channel's 60 Minutes programme that victims had commonly "worked against Russia, focused on Russia, and done extremely well".

The programme also reported that evidence places members of the 29155 unit in cities around the world at times when US personnel experienced Havana Syndrome-type incidents.

The Insider - which collaborated on the investigation - reported that an officer in the 29155 unit had been rewarded for their work developing "non-lethal acoustic weapons".

The Kremlin has dismissed the "unfounded accusations", and plenty scepticism remains - not least because no smoking gun, so to speak, has been found. 

No one is denying that what victims have experienced is, as the NIH scientists put it, "very real...prolonged, disabling and difficult to treat".

Exactly what caused it, however, remains elusive.