'I could see the avalanche coming'

From the beginning, the doctors serving the White House could see the public health threat ahead of them -- but there were some Trump administration officials who "believed this wasn't as a big of deal" as the doctors were making it seem, Dr. Deborah Birx, the White House's coronavirus response coordinator under President Trump, told Gupta.

"First, I wanted to make sure that we stopped saying that the risk to Americans was low," Birx said. "I could see the avalanche coming, and I could see that we were not prepared, and I thought I could do something."

But in the White House, "there was a group that really believed this wasn't as a big of deal as we were making it," she said. "Then there was the other group that just was more fatalistic, that no matter what we did, the outcome was going to be the same."

This division could be seen in some of the White House coronavirus task force's public briefings, especially when it came to wearing masks. Sometimes the doctors were the only officials -- or among the very few -- seen with masks on.

"There was a feeling in the White House from the beginning -- and I don't know if this is true or not because I never confronted the President, because I didn't have access to him by that time -- that the President was not supportive of mask-wearing in the White House," Birx told Gupta.

"There was one event in the Rose Garden, it was made clear that they didn't want us wearing masks," she said. "So all of the Cabinet officials and even some of the military members took their masks off. Dr. Fauci and I did not."

Trump's 'parallel streams of data'

As the pandemic progressed, there were "too many parallel streams of data" about the pandemic being presented Trump, Birx said, also stressing that concern about the US economy seemed to outweigh concern about hospitalizations and deaths.

"I've dealt with Presidents and Prime Ministers around the globe who will often have misperceptions about diseases and the community that that disease impacts. But I've always found that if you can find that common ground with the information and data, they will change policies," Birx told Gupta.

"It's part of the reason why I did say at one time the President looked at the data and understood the data, because he wouldn't have shut down the country for 15 days and then another 30 -- but that never really happened again, because there were too many parallel streams of data," Birx said.

"I know some of them came from his team," Birx said. "I don't know where all of them came from."

CNN reached out to Atlas for comment.

"I told people I would not be in a meeting with Dr. Atlas again," she said. "I felt very strongly that I didn't want an action that legitimized in any way his position."

"Day one when he showed up that was very clear it was written as his view," Admiral Brett Giroir, who served as US Health and Human Services assistant secretary under the former President, told Gupta.

"The subtlety here though is he thought you can protect the vulnerable and let sort of the well build up this herd immunity," Giroir said. "Dr. Birx and I and the rest of the docs said, 'This is a fallacy.' "

The pandemic "was a community spreading event and there was no way to ring-fence vulnerable Americans," Birx said.

'It was reported ... we had a shouting match'

"It was reported in the press that we had a shouting match," Dr. Stephen Hahn, former FDA commissioner, told Gupta. "I can 100% assure you that I did not shout and scream at the secretary of Health and Human Services."

"Did he shout out at you?" Gupta asked.

"You should ask him that question," Hahn replied.

Azar responded in a statement to CNN that "FDA's illegal assertion of jurisdiction over common lab developed tests ... slowed the development of U.S. COVID testing ... Dr. Hahn's recitation of this call is incorrect ... the only intemperate conduct... was Dr. Hahn's threat to resign."

In a response to Azar's statement, Hahn said: "I did not yell on that phone call, and I did not threaten to resign."

Former CDC Director Dr. Robert Redfield also told Gupta that his relationship with Azar was challenging.

"I didn't have really very difficult challenges with the White House. The challenges I had were with the office of the Secretary," Redfield said. "I think some of the ones that were the most notable, that I was the most offended by, was the calls that wanted me to pressure and change the MMWR."

Redfield said that he was asked to change the report "on more than one occasion."

Azar responded in a statement to CNN saying, in part, "Any suggestion that I pressured or otherwise asked Dr. Redfield to change the content of a single scientific, peer-reviewed MMWR article is false."

'I got called by the President'

The pandemic quickly became politicized in the United States.

Birx said that she faced "difficult" consequences for speaking publicly about the threat of the pandemic and its widespread reach to rural communities.

Birx then received what she describes as a "very uncomfortable" and "very difficult" phone call from the former President.

"It was a CNN report in August that got horrible pushback. That was a very difficult time because everybody in the White House was upset with that interview and the clarity that I brought about the epidemic," Birx told Gupta.

"I got called by the President," she said. "It was very uncomfortable, very direct and very difficult to hear."

Gupta asked, "Were you threatened?"

Birx responded, "I would say it was a very uncomfortable conversation."

CNN has reached out to Trump's office for comment on the documentary.

After that, Birx started to give public warnings about the pandemic on a local level because "someone was blocking" her from speaking nationally, she said.

"Were you being censored?" Gupta asked.

"Clearly someone was blocking me from doing it. My understanding is I could not be national because the President might see it," Birx said. "He felt very strongly that I misrepresented the pandemic in the United States, that I made it out to be much worse than it is. I feel like I didn't even make it out as bad as it was."

A pandemic plagued with mixed messages

The nation's doctors were not blind to the mixed messages that the American public has seen during the pandemic -- with some officials claiming the spread of disease was not as bad while others stressed it was much worse.

This was also seen with messaging around masks.

There also was the message from the doctors for people to stay home and for states to shut down. At the same time, the former President called for states to open. That message shocked Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases.

Fauci, now President Joe Biden's chief medical adviser and the only one of the doctors still working in the White House, described Trump's message as "a punch to the chest."

"I said to myself, 'Oh my goodness, what is going on here?' It shocked me because it was such a jolt to what we were trying to do," Fauci told Gupta.

But when the White House coronavirus task force meetings became irregular, behind the scenes, four of the doctors -- Birx, Fauci, Hahn and Redfield -- started their own "doctors' group," as Fauci called it.

"We weren't secret about it. We were pretty open about it. It's just that not very many people knew about it," Fauci told Gupta.

Birx described the group as "important," because her colleagues were attending House and Senate briefings about the pandemic -- and she wanted them armed with the latest data she had available to share with lawmakers.

'I could use the word "cover up" '

Data was hard for US health officials to come by before the coronavirus spread to American soil -- and there could have been a significant benefit to having US investigators on the ground in China to study the virus early in the pandemic, Redfield told Gupta.

"I think we could have learned very quickly that we're dealing with a different beast than the one that everyone had sold us," Redfield said.

He told Gupta that Trump called China's President Xi Jinping, and Azar made requests to China's minister of health -- but none of the outreach helped.

"I still think the most likely aetiology of this pathogen in Wuhan was from a laboratory -- you know, escaped. Other people don't believe that. That's fine. Science will eventually figure it out. It's not unusual for respiratory pathogens that are being worked on in a laboratory to infect a laboratory worker," Redfield told Gupta.

"A year after this pathogen started, we're now having a critical analysis of where it came from by scientists," Redfield said. "It seems to me that some of the information is people are not being transparent about it. I could use the word 'cover up,' but I don't know that so I'm not going to speculate that."

China has denied any cover up.

Gupta asked Fauci, "How big of a difference would it have been if our own investigators had been on the ground in China?"

Fauci said that it would have made a "significant" difference -- and he was "always" skeptical about the Covid-19 data being reported out of China.

"I always had skepticism about it because of what we went through with SARS," Fauci said.

"China was saying, 'Oh it's flu, it's flu,' and then the next thing you know, SARS was all over the world -- in Canada, in Australia, all over the place," he said. "They were not very transparent in the past. It wasn't outright lying. They just didn't give you all the information."

The doctors also agreed that it would have made a difference if the United States was better prepared for what was to come.

'We had no systems in place'

The United States did not know how much emergency supply of personal protective gear, medicines, ventilators and other medical equipment the nation had access to at the start of the pandemic, Dr. Robert Kadlec, former US assistant secretary of Health and Human Services, told Gupta.

The President's criticism also ignored a key point: The stockpile was never intended -- or funded -- to be a panacea for a pandemic. Rather, it serves as one piece of the overall supply chain puzzle during a disaster.

"When we started the pandemic in January, we really didn't know what the status of the supply chain was. We didn't know what hospitals had on hand. We didn't know what the state supplies were. We didn't even know what the commercial distributors had on their shelves," Kadlec told Gupta.

Overall, "we had no systems in place," Giroir told Gupta.

"What's the supply chain? We don't know," Giroir said. "How many tests do we have in the stockpile? Well, there was no test in the stockpile. How many swabs do we have? We didn't have a single swab. So all of this was starting from scratch."

The doctors now hope that the nation is better equipped and more united in its fight against Covid-19.

'All the doctors received death threats'

More than a year after the coronavirus pandemic was declared, there is still divisiveness across the United States, Fauci told Gupta.

"This is a war. So if you're going to fight a war, you better start shooting at the enemy instead of at each other," Fauci said. "I'm nervous about the intensity of the divisiveness in the country right now."

"All the doctors received death threats," Birx told Gupta.

"My daughters got the same rude text messages," she said. "A lot of sexual references, saying, 'The country would be better off if you were dead.' 'You're misleading the country.' 'Your tongue should be cut out.'"

Birx said that she originally would take the threats to the State Department, but eventually "didn't have time."

Former FDA Commissioner Hahn also shared concern about divisiveness in the country.

"We are so divided and there's a lot of mistrust across the board in the US," Hahn told Gupta. "We need to overcome that. We need to come together."