Surgeon General Vivek Murthy issued a warning against health misinformation Thursday, saying that falsehoods spreading quickly online have subjected large numbers of Americans to avoidable illness and death. 

In remarks at the White House, Murthy called on social media companies to step up their efforts on the issue, arguing that technology firms "have enabled misinformation to poison our information environment with little accountability to their users."

"They've allowed people to intentionally spread misinformation - what we call disinformation - to have extraordinary reach," Murthy said of tech companies. "They've designed product features such as 'like' buttons that reward us for sharing emotionally-charged content, not accurate content. And their algorithms tend to give us more of what we click on, pulling us deeper and deeper into a well of misinformation."

The surgeon general's advisory issued by Murthy comes amid a rise in COVID-19 cases, as some Americans resist getting inoculated against the coronavirus despite the widespread availability of vaccinations in the United States.

In March, a coalition of 12 state attorneys general sent a letter to Facebook and Twitter, pressing them to do more to ensure that online falsehoods aren't undermining efforts to vaccinate the public against the coronavirus.

Attorney General William Tong, D-Conn., and 11 other Democratic state attorneys general called on Facebook chief executive Mark Zuckerberg and Twitter CEO Jack Dorsey to "take immediate steps" to fully enforce their policies against vaccine misinformation.

The attorneys general said the companies have not cracked down hard enough on prominent anti-vaccine accounts that repeatedly violate the companies' terms of service.

They also said that falsehoods about the safety of coronavirus vaccines from a small pool of individuals has reached more than 59 million followers on Facebook, YouTube, Instagram and Twitter, citing data from the Center for Countering Digital Hate, which studies online misinformation and disinformation.

A Facebook spokesperson said at the time that the company has worked with health organizations to update its policies and had removed 2 million pieces of content containing coronavirus and vaccine misinformation since February from Facebook and Instagram.

Twitter said in March that it had removed more than 22,400 tweets for violating its policies against coronavirus misinformation since the beginning of the pandemic.

The advisory issued by Murthy on Thursday has a broad list of recommendations. It advises Americans to check whether a source is trustworthy before forwarding information. It also recommends that health and educational institutions work to improve information literacy, and it calls on media organizations not to give a platform to newsmakers who spread misinformation.

But the surgeon general's sharpest words were for tech companies, who he said must operate with greater transparency and accountability. Online misinformation, Murthy said, has led some Americans to resist wearing face masks, turn down medical treatments or choose not to get vaccinated against the coronavirus, factors that have "led to avoidable illnesses and death."

"Simply put, health misinformation has cost us lives," Murthy said.

At Thursday's briefing, Murthy announced that the Rockefeller Foundation has committed to spending $13.5 million to counter health misinformation.

He also revealed the toll the pandemic has taken on his own extended family.

"On a personal note, it's painful for me to know that nearly every death we are seeing now from COVID-19 could have been prevented," Murthy told reporters. "I say that as someone who has lost 10 family members to COVID-19 and who wishes each and every day that they had had the opportunity to get vaccinated."

White House press secretary Jen Psaki said Thursday that a large amount of health misinformation is being spread by a relatively small group of individuals.

"There's about 12 people who are producing 65 percent of anti-vaccine misinformation on social media platforms," Psaki said. "All of them remain active on Facebook, despite some even being banned on other platforms, including … ones that Facebook owns."