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A Canadian scientist's Youtube video about an all natural cancer-curing moss is a social media hit.

But it comes with a twist: the health claims in the video are revealed as completely false.

Jonathan Jarry, its creator, is a science communicator whose career focuses on debunking misinformation like the claims found in his viral video.

The video on the value of scepticism has racked up over nine million views.

Mr Jarry, with McGill University's Office for Science and Society (OSS) in Montreal, said he was inspired to make the video when a former co-worker sent him a Facebook post that claimed cancer could be cured by radio waves.

It was "rife with inaccuracies and omissions" and had been viewed online a whopping six million times, he said.

Evidence-based efforts by OSS, a venture dedicated to promoting critical thinking and the presentation of scientific information to the public, to debunk claims like the radio waves cancer cure theory get barely a fraction of those numbers.

"My idea was let's see if we can build a sort of a Trojan horse," Mr Jarry told the 91�ȱ�.

"And make a video that looks on the outside superficially like one of these easily shareable videos."

He set about cobbling together a video with claims of an "amazing cancer cure" discovered by a Dr Johan R Tarjany in the 1800s that has long been suppressed by the pharmaceutical industry - a unique moss that can alter cancer's DNA.

With upbeat music, savvy editing and claims that sound like they have some scientific basis, he mimicked many viral health videos currently spreading misinformation online.

But halfway through Mr Jarry's video comes the big reveal: there is no Dr Johan R Tarjany and no cancer-curing moss.

It goes on to warn the viewer about how easy it is to get roped into false claims.

"The point is, be sceptical. Ask questions," it warns.

Health misinformation is a serious concern for public health agencies worldwide.

In April, that belief in fake causes of cancer is rife among the public.

In the US, the Food and Drug Administration offers to protect consumers from products claiming to cure cancer online and on social media.

Mr Jarry sees many of the health hoax videos like the one he parodied online and "they spread like wildfire."

"We do have to learn to recognise these bad arguments for what they are," he said.

"They're an appeal to our emotions, to our superficial level of thinking, but they are empty on the inside."

He sees a danger in people potentially delaying medical treatment in favour of the alternative cures on the belief they will work better than modern medicine, or simply spending money on unhelpful treatments.

And he says he is "flabbergasted" at how popular his video turned out to be. He had hoped for a meagre 10,000 shares.