BBC teams are fact-checking some of the most popular fake and misleading coronavirus stories on social media. Jack Goodman and Flora Carmichael bring together what's been debunked this week by BBC Monitoring, Trending and Reality Check.

Fake Facebook posts about The Rock

Thousands of posts have been circulating on Facebook offering huge cash prizes to "help" people financially affected by the coronavirus outbreak.

Although the competition is clearly fake, it is being shared in many languages. Most examples include unrelated video footage or photos of Dwayne Johnson, an actor known as The Rock.

Participants are invited to select a "prize" from a list that corresponds with the first letter of their name. Some people have left bank details in the comments, others ask for financial help.

The most widely shared example we've seen includes a link for people to "collect their prize". It looks like a phishing scam similar to others seen earlier in the coronavirus outbreak. 

A video accompanying one of the posts shows someone handling stacks of money and has had more than four million views.

William Mitchell, who made the original video using fake or "prop" money for his YouTube channel, says it was used without his knowledge. "Ever since I started making prop money videos back in 2018 scammers have been re-uploading my content without my permission," he told the BBC.

Johnson has previously been the subject of similar scams, and in 2018 told his followers: "Be vigilant, be smart, question it, report it… and don't buy into these fake Facebook accounts."

The herbal cure given official approval by a president

The WHO is clear in its advice that there is no medicine currently available that can prevent or cure Covid-19.

However, the president of Madagascar has unveiled what he claims to be a "preventative remedy" this week.

The herbal tonic sold under the name Covid-Organics is derived from artemisia - a plant which contains an ingredient used to treat malaria - along with other plants sourced within the country.

President Andry Rajoelina said tests have been carried out and claimed the remedy had cured two people in Madagascar, the island nation off the east coast of Africa.

There has been no evidence and no peer-reviewed research into its effectiveness against Covid-19.

President Rajoelina announced the partial lifting of quarantine measures on the same day as the launch of the drink.

Local media reports that more than 1,000 soldiers were been deployed to distribute the drink in the capital, Antananarivo.

Video footage shows people queuing for the brew, which is being handed out for free to the most vulnerable locals. It's also being sold in supermarkets.

The Max Planck Institute in Germany is currently testing artemisia against Covid-19 but no results have yet been published.

The Democratic Republic of Congo said it has initiated research into the plant.

Orange peel myth

A video recommending those infected with coronavirus use hot water, orange peel and a vapour rub containing menthol to kill bacteria and release "all the toxins" got over 1.6 million views on the video-sharing site TikTok before being hidden.

It had already been reposted by a popular Instagram account, where it was viewed a further one million times before it was removed.

There is no evidence that hot water or citrus fruits can prevent or cure coronavirus. Inhaling hot steam, also recommended in the video, can be extremely dangerous and there's no evidence that it works.

There have been other examples of misleading information circulating on TikTok. A number of videos spreading conspiracy theories that falsely link 5G to coronavirus have been posted in recent weeks.

As well as supporting 5G conspiracies, some of the videos have encouraged attacks on telephone masts with the hashtag 5Gtowerchallenge and featured harassment of telecommunications workers.

The social media platform has since removed a number of videos of this nature which were flagged to it by BBC News.

A TikTok spokesperson told the BBC: "We do not allow misinformation, including conspiracy theories, which could cause harm to people on TikTok or the wider public."

TikTok also said it was "limiting the searchability of any emerging conspiracy theory-related hashtags".

Aids research is not to blame

An interview with a Nobel-Prize winning scientist who has suggested the coronavirus was created in a laboratory has been widely shared on Facebook.

Luc Montagnier is the co-discoverer of HIV and was interviewed on French TV last week where he claimed the virus was accidentally released from a lab in Wuhan. The virus, he said, is the result of research into an Aids vaccine.

However, despite rampant online speculation, "there is no evidence of any kind that the Sars-CoV-2 virus (which causes Covid-19) was released accidentally from a lab" says BBC science editor Paul Rincon.

Peer-reviewed scientific analysis of the evidence suggests the virus came from animals.

The video has been shared 12,000 times and has clocked up more than 700,000 views after it was posted on the Italian League party's official Facebook page this week.

A plot to control world population

The coronavirus pandemic has been created by "shadow global powers" in an attempt to reduce world population, according to Vladimir Kvachkov, a Russian ex-military intelligence officer in a YouTube interview.

Mr Kvachkov says there is scientific proof the coronavirus was made artificially, but this has been widely dismissed by scientists who say genome sequencing shows that it came from animals.

Uploaded last month, it has had almost nine million views and is still being shared on Facebook in various languages. It was also translated into English this week.

His appearances on other Russian YouTube channels where he talks about the pandemic have generated hundreds of thousands of views.

Additional reporting by Olga Robinson, Alistair Coleman, Marianna Spring, Omega Rakotomalala and Reha Kansara. BBC