In a 2015 speech, Bill Gates warned that the greatest risk to humanity was not nuclear war but an infectious virus that could threaten the lives of millions of people.

That speech has resurfaced in recent weeks with 25 million new views on YouTube — but not in the way that Gates probably intended. Anti-vaccinators, members of the conspiracy group QAnon, and right-wing pundits have instead seized on the video as evidence that one of the world’s richest men planned to use a pandemic to wrest control of the global health system.

Gates, 64, the Microsoft co-founder turned philanthropist, has become the star of an explosion of conspiracy theories about the coronavirus outbreak. In posts on YouTube, Facebook, and Twitter, he is being falsely portrayed as the creator of COVID-19, as a profiteer from a virus vaccine, and as part of a dastardly plot to use the illness to cull or surveil the global population.

The wild claims have gained traction with conservative pundits like Laura Ingraham and anti-vaccinators such as Robert F. Kennedy Jr. as Gates has emerged as a vocal counterweight to President Trump on the coronavirus. For weeks, Gates has appeared on TV, on op-ed pages, and in Reddit forums calling for stay-at-home policies, expanded testing, and vaccine development. And without naming Trump, he has criticized the president’s policies, including this week’s move to cut funding to the World Health Organization.

Misinformation about Gates is now the most widespread of all coronavirus falsehoods tracked by Zignal Labs, a media analysis company. The misinformation includes more than 16,000 posts on Facebook this year about Gates and the virus that were liked and commented on nearly 900,000 times, according to a New York Times analysis. On YouTube, the 10 most popular videos spreading lies about Gates posted in March and April were viewed almost 5 million times.

Gates, who is worth more than $100 billion, has effectively assumed the role occupied by George Soros, the billionaire financier and Democratic donor who has been a villain for the right. That makes Gates the latest individual — along with Dr. Anthony Fauci, the leading US infectious disease expert — to be ensnared in the flow of right-wing punditry that has denigrated those who appear at odds with Trump on the virus.

“Bill Gates is easily transformed into a health-related meme and figure because he’s so well known,’’ said Whitney Phillips, an assistant professor at Syracuse University who teaches digital ethics. “He’s able to function as kind of an abstract bogeyman.’’

This is especially true since Gates has sharpened his comments about the White House’s handling of the coronavirus in recent weeks.

“There’s no question the United States missed the opportunity to get ahead of the novel coronavirus,’’ he wrote in an opinion column in The Washington Post on March 31. “The choices we and our leaders make now will have an enormous impact on how soon case numbers start to go down, how long the economy remains shut down, and how many Americans will have to bury a loved one because of COVID-19.’’

Mark Suzman, chief executive of the Bill & Melinda Gates Foundation, Gates’s main philanthropic vehicle, said it was “distressing that there are people spreading misinformation when we should all be looking for ways to collaborate and save lives.’’

Gates has devoted his time to philanthropic endeavors since he stepped back from the company in 2008. As of 2018, the Gates Foundation had a $46.8 billion endowment, making it one of thelargest private charitable organizations.