For the past week—as the global COVID-19 death toll surpassed 3,800, including at least 22 fatalities in the United States—NBC News has been promoting celebrity doctor Mehmet Oz as the most visible member of the Today show’s so-called “Coronavirus Crisis Team.”

The 59-year-old Oz, an Oprah Winfrey protégé who registered the trademark “America’s Doctor” as his self-awarded title, has been urging Today viewers to vigorously scrub their thumbs and fingertips as part of a 20-second hand-washing ritual to combat the spread of the pandemic, and on Friday, exhorted people over the age of 60—those at highest risk of succumbing to the disease—to stick close to home.

“If I was younger I would go ahead and travel, but if I was older, I wouldn’t—and would avoid crowded places,” Oz told Today co-host Craig Melvin, suggesting that senior citizens keep at an “arm’s length” distance from strangers. “Why take a chance?”

That is prudent counsel, to be sure. (Never mind that it directly contradicted Oz’s recommendation to 88-year-old William Shatner—on Monday’s episode of Access Daily—that the “apprehensive” Star Trek actor proceed with his plans for an international lecture tour: “He can go anywhere he wants. Do not make decisions based on fear… We’ve gotta live our lives.”)

The telegenic Oz might well be a talented thoracic surgeon—best known as the host of the popular syndicated daytime program The Dr. Oz Show—but he is hardly an ideal dispenser of medical advice for an increasingly anxious American public.

“He’s just a quack,” said physician and scientific researcher Henry I. Miller, one of Oz’s more vocal critics in the medical community, but by no means unique in his condemnation of, among other transgressions, Oz’s enthusiastic endorsements of phony weight-loss remedies, his bogus claims of dangerous levels of arsenic in children’s apple juice, and his willingness to provide a platform to the debunked assertion that genetically modified food causes cancer.

“He’s been dishonest and he has been dispensing misinformation to millions now for years,” said Miller, who in 2015 led an unsuccessful campaign to pressure Columbia University’s College of Physicians and Surgeons to fire Oz from its faculty. “I wouldn’t trust any of his observations, and don’t see how he would have responsible and valid views on coronavirus.”

NBC News declined to comment on Oz’s critics or his role on the Today show, where he is one of several paid physician-contributors—but surely the most famous and camera-savvy—who’ve been enlisted in recent days as on-air experts to address viewers’ coronavirus concerns.

In a statement to The Daily Beast, Oz responded: “There are lots of detractors in life who have trouble hearing the truth or engaging in difficult debates about multi-sided topics. I have spent my career with the belief that knowledge is power and I have never shied away from that mantra. We are in the midst of one of the biggest epidemics in recent time and my focus is on educating and calming a fearful public. That’s what we all should be focused on right now.”

Oz and the 72-year-old Dr. Miller—a former Food and Drug Administration official and ex-academic fellow at Stanford University’s conservative-leaning Hoover Institution—are longtime adversaries. On an April 2015 installment of The Dr. Oz Show, Oz countered Miller’s headline-grabbing open letter to Columbia University demanding his dismissal by slamming Miller as a paid shill for the tobacco, pesticide, and genetically modified food industries. (Indeed, Miller was dropped as a columnist by Forbes magazine in 2017 after The New York Times reported that one of his 2015 bylined columns largely echoed a draft prepared by employees of Monsanto.)

In addition, Oz noted that one of the letter’s 10 physician co-signers, Dr. Gilbert Ross, was a convicted felon who served prison time for Medicaid fraud.

Still, most of Oz’s critics are not so easily attacked.

Three Mayo Clinic scientists—Dr. Jon C. Tilburt, M.D., and PhDs Megan Allyse and Frederic W. Hafferty—pulled no punches in their February 2017 article in the AMA Journal of Ethics about the troubling questions raised by Oz’s public influence.

“Should a physician be allowed to say anything—however inaccurate and potentially harmful—so long as that individual commands market share?” they wrote. “In a professional sector whose history and growth is marked by the sustained and rightful denouncement of quacks and quackery… an inability to define and fence the epistemic boundaries of scientific medicine from apparent quackery on such a visible scale becomes something akin to a full-scale identity crisis for medicine…

“Dr. Oz certainly appears to be someone peddling unproven and ineffective remedies for personal gain… Yet, he remains immensely popular, prompting us to wonder, if we can’t effectively sanction Dr. Oz, whom can we sanction?”

Meanwhile, a May 2018 article by Rina Raphael, Fast Company magazine’s health and technology writer, decried Donald Trump’s appointment of Oz to the President’s Council on Sports, Fitness, and Nutrition.

“The inclusion of Dr. Oz took many in the health industry by surprise, especially those who have been following the TV star’s snake-oil antics over the last few years,” Raphael wrote. “Oz has been repeatedly called out for his support of false, deceptive products and unproven medical practices, both from the medical community and consumer watchdog groups.

“His appointment clearly speaks in no way to his reputation as a trusted medical source, but rather to his celebrity status—and the ability to parlay that into multiple business opportunities. Perhaps that’s what Trump, who has shown a preference for pundits over experts, finds appealing.”

More likely, Trump was simply rewarding Oz for letting the then-Republican presidential nominee and his daughter Ivanka onto the Sept. 15, 2016 installment of his syndicated show to tell whoppers, unchallenged, about his physical condition, especially the obvious sham that the obese candidate weighed only 236 pounds. Oz accepted at face value the conclusions of Trump’s discredited doctor, Harold Bornstein, who declared that his patient “will be the healthiest individual ever elected to the presidency.”

“Talk about two snake-oil salesman!” then-Missouri Sen. Claire McCaskill said at the time about Trump’s appearance on Dr. Oz .

“I mean one of them says, ‘Take a pill and you’ll be thin’… from your lips to God’s ear wouldn’t we all love that? Not true. Not medically true. Not scientifically true. And Dr. Oz knows it,” said McCaskill, who famously dressed Oz down for pushing diet scams during a 2014 Senate hearing.

Trump, meanwhile, is “promising things that are totally not true. Lying every time he opens his mouth,” McCaskill added. “So I think it’s really a marriage made in heaven.”

Oz’s legion of critics also includes, but isn’t limited to, New Yorker science writer Michael Specter, the British Medical Journal, and Popular Science magazine.

As of this writing, however, it seems highly doubtful that NBC News and the Today show will spend even a second, much less 20, washing their hands of Dr. Oz.