It started with one doctor. On January 22, Belgian newspaper Het Laatste Nieuws published an interview with Kris Van Kerckhoven, a general practitioner from Putte, near Antwerp. “5G is life-threatening, and no one knows it,” read the headline. One scientifically baseless claim in this article, published in a regional version of the paper’s print edition and since deleted from its website, sparked a conspiracy theory firestorm that has since torn through the internet and broken out into the real world, resulting in fires and threats. Van Kerckhoven didn’t just claim that 5G was dangerous: He also said it might be linked to coronavirus.

Wired UK This story originally appeared on WIRED UK.

At the time, the outbreak was a comparative speck. It had claimed nine lives and infected 440 people, almost all of them in the Chinese city of Wuhan. Under the heading “Link met coronavirus?” the Het Laatste Nieuws journalist pointed out that since 2019 a number of 5G cell towers had been built around Wuhan. Could the two things be related? “I have not done a fact check,” Van Kerckhoven cautioned, before piling in. “But it may be a link with current events.” And so the fuse was lit.

Van Kerckhoven’s comments were quickly picked up by anti-5G campaigners in the Dutch-speaking world, with Facebook pages linking to and quoting from the article. Here, they claimed, was proof of something very dark indeed. Within days, the conspiracy theory had spread to dozens of English-language Facebook pages. But the conspiracy theory that Van Kerckhoven was peddling isn’t new,. It has been bubbling away quietly for decades in unfounded concerns about high-voltage power lines in the 1980s to mobile phones in the 1990s. In coronavirus, such concerns had found a new hook. “Because the quotes were unfounded, we withdrew the article within a few hours,” says Het Laatste Nieuws editor Dimitri Antonissen. “We regret the fact that the story was online for a few hours,” he adds. “Unfortunately with conspiracy theories popping up on several places, this does not stop a story from spreading.” And spread it did.

On YouTube, obscure online talkshow hosts and vloggers started revealing “the truth” about 5G and coronavirus, racking up tens of thousands of views. Posts on Facebook made similarly outlandish claims, receiving only a few thousand views from a familiar and welcoming audience. For some time, the conspiracy theory would bounce across this echo chamber. But some weeks later, it started to break out, propelled by engagement algorithms that were smart enough to spot a viral trend but dumb enough not to notice the idiocy of its content.

From those obscure beginnings, the conspiracy theory has now been pushed by celebrities with hundreds of thousands or millions of social media followers, including boxer Amir Khan, singer Anne-Marie, actor Woody Harrelson, former Dancing on Ice judge Jason Gardiner, pop star Keri Hilson, former Made in Chelsea star Lucy Watston, and TV personality Amanda Holden—the latter of whom claims she “accidentally” tweeted a link to a since-deleted anti-5G petition on Change.org. Said petition, which at the time had more than 110,000 signatures, erroneously claimed that the symptoms of exposure to 5G are “very much” like the symptoms of coronavirus.

In recent days, a number of 5G masts across the UK have been set on fire in apparent arson attacks. According to The Guardian, at least 20 mobile phone masts have been vandalized as a result of 5G disinformation in recent days. Videos of these attacks have gone viral on social media, further adding to the anti-5G fervor. At the government’s daily coronavirus press briefing on April 5, cabinet office minister Michael Gove described the 5G conspiracy theory as “dangerous nonsense,” while the national medical director of the NHS, professor Stephen Powis, said it was “the worst kind of fake news.”