We're fact-checking the week's most popular dubious claims and bringing together the work of BBC journalists investigating coronavirus disinformation.
The White House is not selling commemorative coronavirus coins
A website called the White House Gift Shop has caused anger by selling coins "commemorating" the Covid-19 outbreak for $100 (£80) each.
US Senator Bernie Sanders was one of those infuriated by the coins.
But the White House Gift Shop is a privately run online store with no direct connection to the White House or the Trump administration.
Its own website says it "operates independently of the US government".
The coins, however, do exist and are being sold by the store. They show a coronavirus germ superimposed over a world map, with slogans such as "Together we fought the unseen enemy" and "Everyday heroes suited up". The site says profits will be donated to hospitals.
Set up by President Harry S Truman in 1946, the gift shop was transferred to a private company years ago, which now holds the trademark for "White House Gift Shop".
The site previously came to media attention in 2018 when it sold coins commemorating Donald Trump's Singapore summit meeting with North Korean leader Kim Jong-un.
Californian doctors' misleading lockdown stats
A video in which two American doctors argue for an end to lockdown measures has sparked controversy.
The video of a press conference, broadcast on a local TV station in California, was viewed millions of times on YouTube and Facebook. It was Tweeted by Elon Musk, who has 33 million followers and is becoming increasingly vocal in his opposition to shutdown measures.
In the video Dr Daniel Erickson and Dr Artin Messihi argue for an end to the lockdown based on the data they have collected from their private clinics. They draw sweeping conclusions from their unrepresentative sample, and claim the flu is similar in prevalence and death rates.
It's very hard to establish what proportion of people die after catching coronavirus because no country has yet carried out random testing on a scale that could help us understand how many people actually have it.
You certainly can't do it from the limited data you get from the people who were tested in a few clinics.
The best current estimates are that the Covid-19 death rate is just under 1% and for flu it's 0.1%. These are estimates, which would need large-scale random testing to verify.
On Monday, as the video garnered more views, two professional medical associations, the American College of Emergency Physicians and the American Academy of Emergency Medicine, issued a joint statement condemning the doctors' "reckless and untested musings".
The medical associations said the conclusions reached in the doctors' video were inconsistent with current science and epidemiology regarding Covid-19, adding: "It appears these two individuals are releasing biased, non-peer-reviewed data to advance their personal financial interests without regard for the public's health."
YouTube removed the full video because it violated its policies which were tightened last week.
Bot network exposed
A disinformation campaign against a Chinese businessman who has spoken critically of the Chinese government's response to the coronavirus outbreak has been uncovered.
The campaign, waged through Twitter and Facebook, uses a network of fake accounts, or bots, to target Guo Wengui, an exiled Chinese businessman in the United States.
BBC open source investigator Benjamin Strick identified fake accounts that posted images and text criticising Mr Guo.
A large network of bots would then retweet and comment on the posts to give them trending status using the tags #GuoWengui, and his name written in Chinese.
An army of Chinese & Russian-named bots is attacking a Chinese businessman who has been critical of China's response to #COVID19— Benjamin Strick (@BenDoBrown) April 29, 2020
Over 48hrs I captured tweets on tags #郭文贵 & #milesguo. This THREAD is an #OSINT analysis of how the network operates 🤖👇🤖
cc: @TwitterSafety pic.twitter.com/E8VPbKyPkA
The bots used fake profile pictures and many of them were created on the same day, seemingly with the sole purpose of amplifying the campaign.
Between 27 and 29 April, more than 200 accounts were created on Twitter which only shared media critical of Mr Guo and his views about both China's response to coronavirus in Wuhan, and the number of fatalities in Wuhan.
This is not the first time a campaign has been launched against Mr Guo. He has been the target of disinformation campaigns linked to China since 2017, identified in research from the Australian Strategic Policy Institute.
The discovery of this recent campaign also exposed a large network of multilingual accounts pretending to be Russian, with fake profile photos. The accounts appeared to be automated to promote a pro-Chinese government agenda and other issues.
Twitter has now suspended many of the accounts.
Fake Nobel Prize winner quote
A viral message attributed to Japanese Nobel Prize laureate Tasuku Honjo claims he believes the new coronavirus was "manufactured" in a lab in the Chinese city of Wuhan.
The posts have been shared thousands of times on social media in many languages and recently by the high-profile British businessman, Lord Sugar.
We think the first post was in India and then spread to a Nigerian page where it went viral.
But Prof Honjo, 2018 winner of the Nobel Prize for physiology or medicine, has made no such remarks.
In a statement published on the website of Kyoto University, he said he was "greatly saddened" that his name had been used to spread "false accusations and misinformation".
Scientists say genome sequencing shows that the virus came from animals and was not man-made.
Additional reporting by Alistair Coleman, Olga Robinson, Shayan Sardarizadeh, Wanyuan Song, Marianna Spring and Benjamin Strick.