PROVIDENCE, R.I. (AP) — As the world races to find a vaccine and a cure for COVID-19, there is seemingly no antidote in sight to the burgeoning outbreak of coronavirus conspiracy theories, hoaxes, anti-mask myths and sham treatments.

The phenomenon, unfolding largely on social media, escalated this week when President Donald Trump retweeted a false video about an anti-malarial drug being a cure for the virus and it was revealed that Russian intelligence is spreading disinformation about the crisis through English-language websites.

“It is a real challenge in terms of trying to get the message to the public about what they can really do to protect themselves and what the facts are behind the problem., said Michael Osterholm, head of the University of Minnesota’s Center for Infectious Disease Research and Policy.

“You don’t need masks. There is a cure,” Dr. Stella Immanuel promised in a video that promoted hydroxychloroquine. “You don’t need people to be locked down.”

The truth: Federal regulators last month revoked their authorization of the drug as an emergency treatment amid growing evidence it doesn’t work and can have deadly side effects. Even if it were effective, it wouldn’t negate the need for masks and other measures to contain the outbreak.

None of that stopped Trump, who has repeatedly praised the drug, from retweeting the video. Twitter and Facebook began removing the video on Monday for violating policies on COVID-19 misinformation, but it had already been seen more than 20 million times.

Experts say the flood of bad information is dangerously undermining efforts to slow the virus, which has been blamed for about 150,000 deaths in the U.S.