Since Havana Syndrome emerged in late 2016, the US government has made the mysterious phenomenon an intelligence priority and spent tens of millions of dollars investigating potential microwave weapon attacks by foreign adversaries.
But medical sociology expert Dr Robert Bartholomew is so convinced it's a case of mass delusion, he's co-authored a book on it with Robert Baloh - Havana Syndrome: Mass Psychogenic Illness and the Real Story Behind the Embassy Mystery and Hysteria.
The unexplained illness, which was first recorded in Cuba, has since spread to US embassies across the world (and also some Canadian), with a reported 130 cases. Symptoms include hearing loss, severe headaches, memory issues, dizziness and brain injury.
The Embassy of the United States of America in Cuba, which is where Havana Syndrome was first allegedly encountered
Dr Bartholomew doesn't mince his words. He means what he says and says what he means.
'There is more evidence for Bigfoot than there is for Havana Syndrome,' the US expatriate who is based at the University of Auckland, told Daily Mail Australia.
'The evidence overwhelmingly points to mass hysteria, or as it is commonly referred to by scientists - mass psychogenic illness. Havana Syndrome is a result of incompetent government officials and bad science. I would go so far as to rename it Havana Syndrome Delusion - the absurd belief, in the wake of persistent evidence to the contrary, that diplomats are being targeted with an energy weapon.'
He says it is possible to use noise as a weapon, just not in the way Havana Syndrome victims maintain it is.
'In the Philippines, the government blasted Katy Perry music to break up a demonstration. Other than that, it doesn't work very well because of the laws of physics.'
Katy Perry's music was blasted by the Philippines government to break up a demonstration
Dr Bartholomew says there are four theories as to what causes Havana Syndrome.
Sonic weapon
'The first theory that popped up was that it's a sonic weapon that used soundwaves to make people sick. This one is really far fetched because these people in Havana weren't targeted in the embassy. They were targeted in their homes, and mainly in two big hotels. To target somebody in a huge hotel would defy the laws of physics - 99 per cent of the soundwaves would bounce off the outer wall. It just doesn't work that way.'
Pesticides
'The second explanation was that it was pesticides that were being sprayed to kill mosquitos that were carrying the Zika virus. The problem with that is, there's no neurotoxin in the world that only affects American and Canadian diplomats and their families.'
Frey Effect
'The third explanation is this microwave stuff, the Frey Effect [an auditory phenomenon where microwave or radio frequencies generate clicking sounds inside the head]. This gained popularity after the National Academy of Sciences came out with their report and said it could be the Frey Effect. But they weren't sure. If you look closely at the report, it was just a guess. The person that identified the mechanism in the Frey Effect is Ken Foster at the University of Pennsylvania, he's a bio-engineer. I contacted him and he said it's definitely not the Frey Effect.'
Mass psychogenic illness
'So you're left with the only plausible explanation, which is mass psychogenic illness. The first people infected were intelligence officers on the same small station. This is a defining feature of mass psychogenic illness. It follows social networks and it usually begins in these small, cohesive groups and spreads outwards, and that's exactly what happened. These people all belong to a common work environment. There's a high degree of stress, they're in a foreign country, they knew they were being surveilled 24/7. It's a classic setup for mass hysteria.'
Dr Robert Bartholomew has written a book called Havana Syndrome: Mass Psychogenic Illness and the Real Story Behind the Embassy Mystery and Hysteria.
Dr Bartholomew says mass psychogenic illness has been around for centuries in various forms.
'It used to be called mass or epidemic hysteria. In the past three or four decades it's been called mass psychogenic illness. The phenomena has been around for millennia. There are clear cases dating back to the dancing mania of the middle ages and beyond. I have collected about 3,500 cases going back to the middle ages.
'It started in a small CIA unit in Havana, Cuba in late 2016. And that's exactly what you would expect from mass psychogenic illness. It starts in small, close-knit groups and then spreads from there, usually to
