The claim is made in a Facebook post that reads: “Liz Churchill. The Davos Magicians at the World Economic Forum conveniently had the pre-knowledge of ‘Disease X’. Dr. John Campbell explains that this ‘Disease X’ doesn’t exist in any Medical Textbooks…but yet it appears on the WEF’s website.”

This text matches a tweet by Ms Churchill, a self-described “conspiracy theorist”.

Both posts share a video by retired nurse Dr John Campbell, who has a PhD on nurse education and runs a YouTube channel which has been the subject of fact checks by multiple outlets.

In the video, Dr Campbell refers to a July 2023 article on the WEF website titled “Disease X - this is how we should prepare for the next big virus”.

This preceded a January 2024 panel discussion during WEF's annual conference in Switzerland called "Preparing for Disease X".

During a video of the discussion (five minutes three seconds) World Health Organisation Director General Tadros Adhanom Ghebreyesus says the term 'Disease X' was coined as a placeholder for unknown diseases.

"There are things that are unknown that may happen, and anything happening is a matter of when, not if," he says. "So we need to have a placeholder for that, for the diseases we don't know that may come. And that is when we gave the name Disease X".

In Dr Campbell’s video, which first appeared on YouTube in January 2024, he says he has been through medical textbooks and can find no reference to Disease X.

"Now, Disease X, I've been teaching this sort of thing pretty well full-time since 1990, and I've been a clinical nurse since 1975 … and I'd never heard of this Disease X,” he says.

"All these standard textbooks, not in there so it must be a new disease."

But as made clear by Dr Tedros, Disease X isn't an actual disease. The term represents an unknown pathogen that could emerge in future.

The World Health Organization (WHO) introduced the term in 2018 in its list of priority diseases for research and development in emergency contexts.

The WHO explained Disease X "represents the knowledge that a serious international epidemic could be caused by a pathogen currently unknown to cause human disease".

Professor Edward Holmes, a virology expert at the University of Sydney,  previously told AAP FactCheck that Disease X is "a disease that could emerge in future and cause a human pandemic.”

“It is not a disease that is actively spreading now," he said.

Microbiology and virology expert Paul Young, a professor at the University of Queensland, said the term emerged after the WHO was heavily criticised for not acting fast enough amid the Ebola outbreak 2014-2015.

He has previously explained to AAP FactCheck that the WHO explored how they could better respond to future disease outbreaks, which included crafting the list of pathogens that may emerge as the next pandemic, such as Ebola and Zika virus.

These were to become priorities for global efforts to develop intervention strategies such as vaccines.

The WHO added “Disease X” to this list to represent any unknown future pathogen, he said.

SARS-CoV-2, the virus that causes COVID-19, became the first example of a Disease X that emerged after the list was published and there would no doubt be more, Prof Young said.

"The spillover of microbes from animals to humans (and the other way) happens more often than many people realise," he added.

Kate Kelland, health writer and author of the book “Disease X — The 100 Days Mission to End Pandemics”, previously told AAP FactCheck that Disease X is hypothetical.

"It’s not a real disease or an actual virus, but it is a very real threat."

Similar claims have been debunked previously by AAP FactCheck, Reuters, The Associated Press, Factcheck.org and AFP.