During the outset of the pandemic, when Americans were frightened and confused about how to protect themselves from the deadly virus, President Trump held a news conference where he added his non-scientific opinion as to what people should do to avoid catching the highly contagious COVID. Trump believed in his deep knowledge of science because, he once said, he had an uncle who taught at MIT.

The New York Times reported that Trump’s suggestion about how to avoid COVID caused a large public response, as well as warnings from public health agencies:

WASHINGTON — In Maryland, so many callers flooded a health hotline with questions that the state’s Emergency Management Agency had to issue a warning that “under no circumstances” should any disinfectant be taken to treat the coronavirus. In Washington State, officials urged people not to consume laundry detergent capsules. Across the country on Friday, health professionals sounded the alarm.

Injecting bleach or highly concentrated rubbing alcohol “causes massive organ damage and the blood cells in the body to basically burst,” Dr. Diane P. Calello, the medical director of the New Jersey Poison Information and Education System, said in an interview. “It can definitely be a fatal event.”

Even the makers of Clorox and Lysol pleaded with Americans not to inject or ingest their products.

The frantic reaction was prompted by President Trump’s suggestion on Thursday at a White House briefing that an “injection inside” the human body with a disinfectant like bleach or isopropyl alcohol could help combat the virus.

“And then I see the disinfectant, where it knocks it out in a minute,” Mr. Trump said after a presentation from William N. Bryan, an acting under secretary for science at the Department of Homeland Security, detailed the virus’s possible susceptibility to bleach and alcohol.

“One minute,” the president said. “And is there a way we can do something like that, by injection inside or almost a cleaning? Because you see it gets in the lungs and it does a tremendous number on the lungs. So it would be interesting to check that.”

Dr. Deborah L. Birx, the White House’s coronavirus response coordinator, was sitting to the side in the White House briefing room, blinking hard and looking at the floor as he spoke. Later, Mr. Trump asked her if she knew about “the heat and the light” as a potential cure.

“Not as a treatment,” Dr. Birx said, adding, “I haven’t seen heat or light —” before the president cut her off.

Mr. Trump’s remarks caused an immediate uproar, and the White House spent much of Friday trying to walk them back. Also Friday, the Food and Drug Administration warned that hydroxychloroquine and chloroquine, two drugs that the president has repeatedly recommended in treating the coronavirus, can cause dangerous abnormalities in heart rhythm in coronavirus patients and has resulted in some deaths.

Later, Trump insisted he was being sarcastic, not serious.

After Trump’s press conference, reports to poison control centers spiked.

Time magazine reported on a bulletin from the American Association of Poison Control Centers, which held that reports of poisoning from ingesting bleach and other disinfectants rose after Trump’s remarks.

The Hill reported a sharp increase in calls to poison control centers after Trump made his remarks.

The Michigan Poison Center reported an increase in calls to poison centers in at least five states after Trump’s remarks. The makers of Clorox and Lysol issued statements urging the public not to ingest their products.

The Harvard Business Review published an article asserting that we can never know for sure how many people drank bleach and how many died, because so many people who answer survey questions don’t understand the question or the answer.

The NIH concluded that no one died of ingesting bleach because 100% of those surveyed gave answers to the questions that were silly, mischievous, or ignorant. The author of the Harvard Business Review article was a contributing author to the NIH study.

Politico posted a reminiscence of the day that Trump recommended ingesting bleach exactly one year later, when he was no longer in office.

One year ago today, President Donald Trump took to the White House briefing room and encouraged his top health officials to study the injection of bleach into the human body as a means of fighting Covid. It was a watershed moment, soon to become iconic in the annals of presidential briefings. It arguably changed the course of political history.

Some ex-Trump aides say they don’t even think about that day as the wildest they experienced — with the conceit that there were simply too many others. But for those there, it was instantly shocking, even by Trump standards. It quickly came to symbolize the chaotic essence of his presidency and his handling of the pandemic. Twelve months later, with the pandemic still lingering and a U.S. death toll nearing 570,000, it still does.

“For me, it was the craziest and most surreal moment I had ever witnessed in a presidential press conference,” said ABC’s chief Washington correspondent Jon Karl, who was the first reporter at the briefing to question Trump’s musings about bleach.

For weeks, Trump had been giving winding, stream-of-consciousness updates on the state of the Covid fight as it clearly worsened. So when he got up from the Oval Office to brief reporters gathered in the James S. Brady Press Briefing Room on April 23, there was no expectation that the day’s proceedings would be any different than usual.

Privately, however, some of his aides were worried. The Covid task force had met earlier that day — as usual, without Trump — to discuss the most recent findings, including the effects of light and humidity on how the virus spreads. Trump was briefed by a small group of aides. But it was clear to some aides that he hadn’t processed all the details before he left to speak to the press.

“A few of us actually tried to stop it in the West Wing hallway,” said one former senior Trump White House official. “I actually argued that President Trump wouldn’t have the time to absorb it and understand it. But I lost, and it went how it did.”

Trump started his press conference that day by doing something he’d come to loathe: pushing basic public safety measures. He called for the “voluntary use of face coverings” and said of his administration, “continued diligence is an essential part of our strategy.”

Quickly, however, came a hint at how loose the guardrails were that day. Trump introduced Bill Bryan, head of science and technology at the Department of Homeland Security. “He’s going to be talking about how the virus reacts in sunlight,” the president said. “Wait ‘til you hear the numbers.”

As Bryan spoke, charts were displayed behind him about surface temperatures and virus half-lives. He preached, rather presciently, for people to “move activities outside” and then detailed ongoing studies involving disinfectants. “We tested bleach,” he said at one point. “I can tell you that bleach will kill the virus in five minutes.”

Standing off to the side, Trump clasped his hands in front of his stomach, nodded and looked out into the room of gathered reporters. When Bryan was done, he strode slowly back to the lectern.

“A question that probably some of you are thinking of if you’re totally into that world,” Trump began, clearly thinking the question himself, “So, supposing we hit the body with a tremendous — whether it’s ultraviolet or just very powerful light — and I think you said that that hasn’t been checked, but you’re going to test it. And then I said, supposing you brought the light inside the body, which you can do either through the skin or in some other way, and I think you said you’re going to test that, too. It sounds interesting. And then I see the disinfectant, where it knocks it out in a minute. One minute. And is there a way we can do something like that, by injection inside or almost a cleaning. Because you see it gets in the lungs, and it does a tremendous number on the lungs. So it would be interesting to check that.”

Dr. Deborah Birx, Trump’s former coronavirus response coordinator, sat silently off to the side as the president made these suggestions to her. Later, she would tell ABC, “I didn’t know how to handle that episode,” adding, “I still think about it every day.”

Inside the Biden campaign, aides were shocked as well. They were working remotely at that juncture, communicating largely over Signal. But the import of what had happened became quickly evident to them.

“Even for him,” said one former Biden campaign aide, “this was stratospherically insane and dangerous. It cemented the case we had been making about his derelict covid response.”

In short order, the infamous bleach press conference became a literal rallying cry for Trump’s opponents, with Biden supporters dotting their yards with “He Won’t Put Bleach In You” signs. For Trump, it was a scourge. He would go on to insist that he was merely being sarcastic — a claim at odds with the excited curiosity he had posing those questions to Birx. His former team concedes that real damage was done.

“People joked about it inside the White House like, ‘Are you drinking bleach and injecting sunlight?’ People were mocking it and saying, ‘Oh let me go stand out in the sun, and I’ll be safe from Covid,” said one former administration official. “It honestly hurt. It was a credibility issue. … It was hurting us even from an international standpoint, the credibility at the White House.”

That Trump was even at the lectern that day was head-scratching for many. For weeks, he and his team had downplayed the severity of the Covid crisis even as the president privately acknowledged to the Washington Post’s Bob Woodward that it had the potential to be catastrophic. But as it became clearer that the public was not buying the rosy assessments, Trump had decided to take his fate into his own hands — assembling the press on a daily basis to spin his way through the crisis.

He loved it. The former administration official said Trump was elated with the free airtime he was getting on television day after day. “He was asking how much money that was worth,” the aide recalled. The coverage was so ubiquitous that, at one point, Fox News’ Bret Baier attended the briefing and peppered the president with questions because his own show was being routinely interrupted.

The bleach episode changed all that.

Aides immediately understood what a public health quagmire Trump’s remarks had created. White House press secretary Kayleigh McEnany insisted he was being taken out of context.

“President Trump has repeatedly said that Americans should consult with medical doctors regarding coronavirus treatment, a point that he emphasized again during yesterday’s briefing,” McEnany said in a statement issued the next day. “Leave it to the media to irresponsibly take President Trump out of context and run with negative headlines.”

His aides realized that it was not a good strategy for him to present medical advice to the public, but Trump loved the attention.