When he first learned he had tested positive for the coronavirus, President Donald Trump was already aboard Air Force One, en route to a massive rally in Middletown, Pa.

With him on the plane that Saturday evening were dozens of people — senior aides, Air Force One personnel, junior staffers, journalists and other members of the large entourage typical for a presidential trip — all squeezed together in the recirculating air of a jetliner.

“Stop the president,” White House physician Sean Conley told chief of staff Mark Meadows, according to a new book by Meadows set to publish Tuesday that was obtained by the Guardian newspaper. “He just tested positive for covid.”

But Meadows asserts in his book that it was too late to stop Trump, and that a second rapid antigen test — apparently done using the same sample — came back negative. But under guidelines from the Centers for Disease Control and Prevention, Trump should have taken a more accurate polymerase chain reaction (PCR) test to confirm whether he had covid-19.

“Had I been there, and Dr. Conley would have told me they would have received a positive test, I would have assumed it was accurate and frankly canceled everything right away,” said John F. Kelly, one of Trump’s previous chiefs of staff, adding that he also would have rushed Trump to Walter Reed National Military Medical Center. “To do anything else would be irresponsible.”

In fact, Trump was hospitalized at Walter Reed about a week later. From the day he tested positive until his hospitalization, Trump came in contact with more than 500 people, either those in proximity to him or at crowded events, not including rallygoers, according to a Washington Post analysis of the president’s interactions during that period.

That seven-day window reveals a president and chief of staff who took a reckless, and potentially dangerous, approach to handling the coronavirus, including Trump’s own positive test.

Trump and Meadows hid Trump’s positive test not just from the public, but also from his inner circle and from his top public health officials. He took part in a debate with Democratic rival Joe Biden three days later, never revealing the test result to Biden or event organizers.

And Trump took no extra precautions, such as mask-wearing or social distancing, to protect those he came in contact with in the days following the positive test.

By the end of October, more than two dozen people in Trump’s orbit would test positive for the coronavirus.

According to the official narrative of the Trump White House, the president first tested positive for the virus on the evening of Thursday, Oct. 1, and was taken by helicopter to Walter Reed less than 24 hours later. But medical experts say that a more likely time frame is at least a week between an initial positive test and a patient requiring hospitalization.

“It would make more sense that you would test positive and then a lot of patients we see hospitalized end up hospitalized on Day 10 or that second week, when the inflammatory response of the immune system is taking over,” said Abraar Karan, an infectious-disease doctor and global health researcher at Stanford University. “Let’s say you’re exposed today. You may not test positive for three to five days because the virus is in its early stages incubating, so that first week, you’re testing positive, but it’s really in that second week — seven, 10, 14 days out — that you could have more severe symptoms from inflammatory response.”

In a statement Wednesday, Trump denied Meadows’s account and Meadows tried to walk back the news in his book, saying through a spokesman that “the book is quite clearly referring to a ‘false positive’ rapid test the president received.” He also claimed that after the initial positive test, Trump “received multiple confirmatory tests that came back negative,” although Meadows describes only one negative test in his book, according to the Guardian account.

There is no way of knowing whether the initial Sept. 26 coronavirus test was a false positive or, rather, the first true indicator of the virus that would fell Trump days later. Both Meadows and Trump have previously misled the public on a host of issues, including Trump’s covid status. Meadows declined to comment further through a spokesman, and a Trump spokesman did not respond to a request for comment.

Either way, Meadows writes, Trump took the second negative test as “full permission to press on as if nothing had happened.”

Trump continued onto the rally of thousands, where he barely discussed the virus, referring to it at times as the “China virus” and the “plague from China.”

On the return trip home, Trump ventured back to the press cabin — unmasked — where he spoke with the media for roughly 10 minutes off the record. One of the reporters on Air Force One that day, Michael Shear of the New York Times, would test positive for the coronavirus less than a week later. Two other members of the White House press corps tested positive the same day as Shear, according to reports.

And even Meadows, on the day Trump first received the test he claims was a false positive, seemed to sense something was amiss. In his book, he describes Trump as looking “a little tired,” explaining that he assumed the president had a “slight cold.”

Saturday, Sept. 26: “It’s going to be extremely noncontroversial”

Trump began his Saturday with a private indoor meeting of evangelical leaders. But the real excitement, for Trump, came later in the day: a Rose Garden ceremony to announce his nomination of Amy Coney Barrett to the Supreme Court.

Just after 5 p.m., to the strains of “Hail to the Chief,” Trump strode into the Rose Garden. The crowd of roughly 150 people — many maskless — stood and cheered when Trump announced Barrett’s name, before he extolled his high court pick for about 10 minutes.

At one point, Trump joked, “It’s going to be extremely noncontroversial.”

Afterward, a number of guests filed back into the White House for a private reception, including some who joined at the last minute. Trump and first lady Melania Trump also met with Barrett, her husband, six of their children, and Vice President Mike Pence and his wife, Karen, in the Oval Office, none of them wearing masks.

Trump then left the White House for his campaign rally in Pennsylvania, stopping first to speak to the press on the South Lawn. It was just after Marine One lifted off, at 6:35 p.m., that Meadows received the call from Conley warning that Trump had just tested positive.

Several White House advisers who attended the Barrett event said attendees were never told that Trump had received a positive test after the event.

Meadows claims in his book that he “instructed everyone in his immediate circle to treat him as if he was positive,” but he did not tell aides in Trump’s immediate orbit that Trump had received a positive test, according to several former senior Trump officials who said they should have been alerted.

Neither Pence — who attended the Rose Garden ceremony Saturday — nor his team was told that Trump had tested positive that day, according to a former senior administration official with direct knowledge of the matter. Pence continued to interact with Trump in the following days.

The Rose Garden ceremony would later become known as an apparent superspreader event, with more than a half dozen attendees testing positive for the coronavirus within the week — including Trump, his wife, former New Jersey governor Chris Christie, counselor to the president Kellyanne Conway, Notre Dame President John Jenkins, and Republican Sens. Mike Lee (Utah) and Thom Tillis (N.C.).

Overall, Trump came in contact with roughly 150 people that Saturday, according to The Post’s analysis.

Sunday, Sept. 27: “Obviously it’s a dangerous thing”

Trump spent Sunday morning golfing at Trump National Golf Club in Virginia. Anti-Trump protesters stood outside holding signs noting the mounting death toll from covid: 200,000 Americans and counting.

Later in the day, Trump held a 37-minute news conference in the White House briefing room, sans mask.

He also hosted an event in the East Wing for Gold Star families who have lost loved ones to military combat. Attendees included Pence and his wife; Gen. Mark A. Milley, chairman of the Joint Chiefs of Staff; and Adm. Charles W. Ray, then the vice commandant of the Coast Guard, who tested positive for the coronavirus on Monday, Oct. 5.

Later, after Trump’s hospitalization, the president seemed to blame the Gold Star families for possibly giving him the virus.

“They tell me these stories, and I can’t say, ‘Back up, stand 10 feet away,’ you know? I just can’t do it. And I went through like 35 people, and everyone has a different story,” Trump said in an interview on Fox News, referring to the Gold Star event. “They come within an inch of my face sometimes, they want to hug me and they want to kiss me. And they do. And frankly, I’m not telling them to back up. I’m not doing it, but obviously it’s a dangerous thing, I guess, if you go by the covid thing.”

Kelly, Trump’s former chief of staff, said his behavior was irresponsible.

“You don’t want him infecting other people, whether it’s Gold Star families, members of the Cabinet, or Secret Service, the staff, or anyone else around him,” Kelly said.

Trump came in contact with roughly 70 people that Sunday, according to The Post’s analysis.

Monday, Sept. 28: “Hope you don’t test positive”

Just before 11 a.m. on Sept. 28, 13 reporters were invited to watch Trump inspect a silver Lordstown Motors 2021 electric pickup on the South Lawn. Other attendees included a senior White House adviser, one senator, one congressman and three Lordstown Motors employees.

Later in the afternoon, Trump and Pence held a Rose Garden event to discuss the admiration’s plans for combating the coronavirus. The men were joined by 11 top administration officials, as well as a governor, two state lawmakers and the executive of a coronavirus testing company.

“Somewhat ironically, considering his circumstances,” Meadows wrote in his book, according to the Guardian, Trump’s remarks included a new testing strategy that was “supposed to give quicker, more accurate readings about whether someone was positive or not.”

As he introduced Adm. Brett Giroir, the White House coronavirus testing coordinator, Trump joked, “Good luck. Hope you don’t test positive.”

Trump came in contact with roughly 30 people that Monday, according to The Post’s analysis.

Tuesday, Sept. 29: “I don’t wear masks like him”

The Tuesday morning of the first presidential debate, Trump huddled at the White House with his debate prep team, a group of roughly 10 senior advisers and outside confidants.

In his book, Meadows describes Trump as looking slightly better than he did on the day of his positive test, but with an “emphasis on the word slightly.”

“His face, for the most part at least, had regained its usual light bronze hue, and the gravel in his voice was gone,” Meadows writes. “But the dark circles under his eyes had deepened.”

In midafternoon, Trump traveled to Cleveland for the debate, joined aboard Air Force One by at least 13 staff, family members and confidants, and was greeted at the airport by four Ohio state representatives.

One adviser who traveled with Trump to the debate said they had no knowledge about the president testing positive for the coronavirus several days earlier. Trump was not wearing a mask either during debate prep earlier in the day or on Air Force One, and did not mention his positive test, this person added.

“As we walked into the venue around five o’clock in the evening, I could tell that he was moving more slowly than usual,” Meadows writes of Trump. “He walked like he was carrying a little extra weight on his back.”

The candidates relied upon what Fox News’s Chris Wallace, the debate moderator, later described as “an honor system” for coronavirus tests.

Once inside the debate hall — which had an audience of about 80 people — many of the guests on Trump’s side, including his family, refused to wear masks. That was in violation of the debate rules that requested masks for all attendees. They even declined masks offered by doctors from the Cleveland Clinic, which was overseeing the debate’s testing protocol.

The debate, which began just after 9 p.m., was fiery from the start, with Trump repeatedly interrupting Biden and Wallace.

At one point, Trump mocked Biden for his insistence on mask-wearing. “I don’t wear masks like him,” Trump quipped. “Every time you see him, he’s got a mask. He could be speaking 200 feet away from them, and he shows up with the biggest mask I’ve ever seen.”

Alyssa Farah, the former White House communications director, told The Post that at the time, she had asked senior staff, including Meadows, when Trump was last tested before the debate. But Conley and Meadows told her not to share with the public when Trump was last tested and declined to tell even her, she said.

Trump’s Sept. 26 positive test, she said, “was clearly withheld from me because I would have been among the senior staff who were around him. I was constantly in proximity. I should have been contact traced.”

“It just demonstrates a disregard for the well-being of others,” Farah said.

Trump came in contact with roughly 20 people that Tuesday, according to The Post’s analysis.

Wednesday, Sept. 30: “We got tremendous reviews on it”

The day after the debate marked the first inkling in Trump’s orbit that something was wrong.

The day started with an Oval Office meeting between Trump and Treasury Secretary Steven Mnuchin. Later, Trump left the White House to fly to Minnesota for a fundraiser attended by about 40 people, followed by a rally in Duluth.

Trump again mocked Biden at the rally for holding socially distanced events and for criticizing Trump’s larger, non-socially distanced rallies. But Trump wrapped up his remarks after just 45 minutes, a notably short performance for him.

During the rally, Hope Hicks, a top Trump aide and close confidante, had started feeling sick. By the time she boarded Air Force One, she discreetly self-quarantined, exiting the plane from the rear entrance when it touched down just after midnight.

Trump came in contact with roughly 55 people that Wednesday, according to The Post’s analysis.

Thursday, Oct. 1: “Whether we have it, we don’t know”

Hicks reported to work on Thursday morning, where — confirming her suspicions — she tested positive. She went home to isolate, telling only Trump and a small cadre of top staff, including Meadows.

Later in the day, Trump was scheduled to travel to his golf club in Bedminster, N.J., for a roundtable and fundraiser. Despite knowing that Hicks — who had been in regular and close contact with the president — was sick, the White House decided to go ahead with the event and did not alert attendees in advance about the president’s exposure.

On the way to the fundraiser, Trump did not wear a mask on Marine One or around aides, said someone familiar with his actions that day. This person added that several of the staff members who flew on Marine One with Trump did not even know Hicks had tested positive when they boarded.

The roundtable, which included roughly two dozen attendees, was indoors. But the main fundraiser, which had 207 invitees, according to a list provided to The Post, was outside at his golf course.

At the time, some attendees said Trump seemed like himself, but others thought he appeared a bit tired. He departed Bedminster notably early — “about 30 minutes ahead of schedule,” according to a media report — spending less than two hours on the property.

At some point in this period, Trump tested positive for the coronavirus. Then Bloomberg News broke the news of Hicks’s illness at 8 p.m.

Trump was scheduled to appear on Sean Hannity’s Fox News show by phone. Despite having known about Hicks’s diagnosis for several hours, Trump behaved as if he was surprised — and said nothing of his own positive result.

“She did test positive,” Trump said. “I just heard about this.”

He then told the host that he and Melania were getting tested.

“So whether we quarantine, or whether we have it, we don’t know,” Trump said.

Trump came in contact with roughly 200 people that Thursday, according to The Post’s analysis.

Friday, Oct. 2: “Tonight, @FLOTUS and I tested positive for COVID-19”

Trump began his Friday with a surprise tweet just before 1 a.m.: “Tonight, @FLOTUS and I tested positive for COVID-19,” the president wrote. “We will begin our quarantine and recovery process immediately. We will get through this TOGETHER!”

The campaign canceled Trump’s rally for that evening in Florida, but throughout the day, White House staff repeatedly claimed that Trump — who remained out of public view — was healthy and strong.

Meadows described Trump to reporters as “in good spirits,” exhibiting only “mild symptoms,” and “very energetic.”

White House press secretary Kayleigh McEnany similarly claimed that Trump was “hard at work, despite the mild symptoms.”

But by late afternoon, McEnany released a statement saying that “out of an abundance of caution,” Trump would travel to Walter Reed. A mask-clad Trump exited the White House from the Diplomatic Room entrance at 6:16 p.m., giving a thumbs-up and brief wave, before walking to Marine One on his own.

It would later emerge that Trump’s condition was far more perilous than the White House acknowledged at the time.

One former senior administration official, speaking anonymously to share a candid opinion, remarked, “Everyone spent months trying to reconstruct the Rose Garden and it turns out it was good old Patient Zero, the president.”

Trump came in contact with very few people that Friday, according to The Post’s analysis. By then, the entire world knew he had covid-19.