In a 22-page advisory, his first as President Joe Biden’s surgeon general, Murthy wrote that bogus claims have led people to reject vaccines and public health advice on masks and social distancing, undermining efforts to end the coronavirus pandemic and putting lives at risk.

The warning comes as the pace of COVID-19 vaccinations has slowed throughout the U.S., in part because of vaccine opposition fueled by unsubstantiated claims about the safety of immunizations and despite the U.S. death toll recently passing 600,000.

Murthy, who also served as surgeon general under President Barack Obama, noted that surgeon general advisories have typically focused on physical threats to health, such as tobacco. Misinformation about COVID-19, deemed an “infodemic” by the World Health Organization, can be just as deadly, he said.

“Misinformation poses an imminent and insidious threat to our nation’s health,” Murthy said during remarks to reporters Thursday at the White House. “We must confront misinformation as a nation. Lives are depending on it.”

Given the role the internet plays in spreading health misinformation, Murthy said technology companies and social media platforms must make meaningful changes to their products and software to reduce the spread of misinformation while increasing access to authoritative, fact-based sources.

Too often, he said, the platforms are built to encourage, not counter, the spread of misinformation.

“We are asking them to step up,” Murthy said. “We can’t wait longer for them to take aggressive action.”

The criticism is not new, and Facebook, YouTube, Twitter and other platforms have defended their work to stem the tide of misinformation. In a response to Murthy, Twitter noted that it has removed more than 40,000 pieces of content that violated its COVID-19 misinformation rules.

“We agree with the surgeon general,” Twitter said in a statement. “Tackling health misinformation takes a whole-of-society approach.”

Murthy’s recommendations went beyond tech firms. Teachers, he said, should expand lessons on media literacy and critical thinking. Journalists, he suggested, should work to responsibly debunk health misinformation without inadvertently spreading it further. And public health professionals, he added, should do a better job answering questions and explaining why public health guidelines sometimes change based on new information.

As for everyday Americans, Murthy urged them to verify questionable health information with trusted sources like the U.S. Centers for Disease Control and Prevention and to exercise critical thinking when exposed to unverified claims. If people have loved ones or friends who believe or spread misinformation, he said, it’s best to engage by listening and asking questions rather than by confronting them.

While some groups that push health misinformation do so for profit or other motives, many Americans may be spreading false information without realizing it, according to the advisory.

“Misinformation hasn’t just harmed our physical health — it has also divided our families, friends, and communities,” Murthy wrote in the advisory. “The only way to address health misinformation is to recognize that all of us, in every sector of society, have a responsibility to act.”