A Fox News commentator has stoked outrage by comparing Dr Anthony Fauci, Joe Biden's chief medical adviser, to Josef Mengele, the Nazi "Angel of Death".
The news comes amid fears that the new Omicron variant will trigger a new wave of Covid cases and further deepen political divisions in the US over how to respond to the pandemic. Fox News has consistently given a platform to misinformation about Covid and measures meant to contain it.
Bill Grueskin, a professor at Columbia Journalism School, responded: "The real issue isn't [Lara] Logan's insanity. It's the complicity of Pete Hegseth, the Fox News host. He never interrupts or pushes back. It's just another day at the office."
Fauci, 80, has served seven presidents as head of the National Institute of Allergy and Infectious Diseases since 1984.
Last weekend, he told CBS he dealt with rightwing attacks, including death threats, "by focusing on what my job is from the time that I went into medicine to right now.
"Where I am at my age, my job has been totally focused on doing what I can with the talents and the influence I had to make scientific advances to protect the health of the American public."
More than 778,000 people have died in the US from Covid-19, many from the Delta virus variant. Omicron was discovered in South Africa. It has not been detected in the US but Fauci and other government scientists have said it is likely to be present.
The danger from Omicron is not clear but the World Health Organization has issued warnings about transmissibility and potential reaction to vaccines. On Monday, Biden said Americans should be concerned but should not panic.
Hegseth asked Logan: "What's your take on where we are, where we're going?"
"Well, it's very simple, Pete," said Logan. "You just have to look at Africa. They didn't have the death rates from Covid that were predicted. And what is happening over time, is that the entire response to Covid and everything that we were told about it from the beginning, is being exposed and it's falling apart, the lies are coming apart.
"And really now there's no justification for putting people out of their jobs or forcing vaccine mandates for a disease that ultimately is very treatable … and has death rates that compare very much to seasonal flu.
"And so in that moment, what you see on Dr Fauci, this is what people say to me, that he doesn't represent science to them. He represents Josef Mengele, Dr Josef Mengele, the Nazi doctor who did experiments on Jews during the second world war and in the concentration camps, and I am talking about people all across the world are saying this."
Mengele escaped justice after the second world war, dying under an assumed identity in Brazil in 1979.
Hegseth and another guest, the Fox News host Will Cain, did not respond to Logan's remark about Mengele. Fox News did not respond to a request for comment.
Claiming responses to Covid had affected "civil liberties, the suicide rates, the poverty, it has obliterated economies", Logan added: "People see that there's no justification for what has been done.
"So as [scientists like Fauci are] being exposed and the control is slipping away, lo and behold, another variant surfaces, and nobody should be surprised by that because there will be more variants until the end of time. We'll never be free of them."
Logan's baseless claim that the Omicron variant is made-up echoed a rightwing talking point voiced, in varying forms, by figures including the former White House doctor turned Texas congressman Ronny Jackson.
Logan rose to fame with CBS as a hard-hitting reporter during the Iraq war and the Arab spring of 2011. In Egypt that year she was assaulted while reporting from Tahrir Square.
After leaving CBS in 2013, over errors in a report about the deadly attack on a US compound in Benghazi, Libya, the year before, she moved into rightwing media. Her show on Fox Nation is called Lara Logan Has No Agenda.