WASHINGTON — Until this week, Dr. Anthony Fauci was a near-constant presence at the daily coronavirus task force briefings at the White House. As the head of the National Institute of Allergy and Infectious Diseases for 35 years, his expertise on the global pandemic has been a reassuring force for millions of Americans concerned about how COVID-19 has uprooted their lives.

Of the roughly 50 press conferences on the health crisis so far, Fauci had only missed a handful. But now, for the first time since regular press conferences began on the topic, Fauci was only present for one of seven briefings this week.

While Fauci gave media interviews throughout the week, his absence at the podium Friday was notable given the president’s controversial remarks a day earlier about using light and disinfectants to possibly treat the deadly respiratory illness.

And though Fauci regularly shares his decades-long infectious disease knowledge publicly, one administration official suggested there’s a preference that Fauci do more of that behind closed doors so it doesn’t appear he’s on such a different page from the president.

“You are here in a certain role, you’ve got to give advice privately,” this official said.

Members of the president’s task force have taken notice of Fauci’s diminished public profile, as well. There is mounting frustration among some of them with Fauci, who has, at times, publicly contradicted President Trump. Adding to the tensions, some officials complain they feel caught off guard by some of Fauci’s media interviews.

When asked why he was only at the briefing once this week, an administration official tells NBC News that Fauci "does have other responsibilities at NIH. Just because he is not at the briefing does not mean he’s not actively involved in task force meetings and briefings."

White House Deputy Press Secretary Judd Deere was more direct, telling NBC News that "despite the media’s ridiculous efforts to somehow create distance between the president and his top health experts, it is simply fake news."

"President Trump has relied on and consulted with Dr. Adams, Dr. Birx, Dr. Fauci, Dr. Hahn, Dr. Redfield, and many others," Deere added, "as he has confronted this unforeseen, unprecedented crisis and put the full power of the federal government to work to slow the spread, save lives, and place this great country on a data-driven path to opening up again."

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The most recent example of discord came on Thursday when an interview with “TIME” revealed the doctor had a dismal view of the country’s testing capability.

“We absolutely need to significantly ramp up, not only the number of tests but the capacity to actually perform them,” Fauci said. “I am not overly confident right now at all that we have what it takes to do that.”

When asked later in the day if he agreed with Fauci, the president said: “I don't agree with him on that, no, I think we're doing a great job on testing.”

On Wednesday, the only day Fauci joined for the briefing this week, he refuted the president’s assertion that coronavirus “may not come back at all” this year and, if it does, it would just be “embers” or “pockets.” Minutes later, Fauci took to the lectern to state definitively: “We will have coronavirus in the fall. I am convinced of that.”

While Fauci has appeared on most Sunday shows through March and April, he did not appear last weekend and is not currently slated to be on any of the political programs in the coming days.

Given Fauci’s absence from the briefings this week, several of the president’s aides and allies have started to wonder what it means about their relationship. Officials close to the task force, however, insist Fauci’s role is seen as critical to the pandemic response and maintain his job is safe.

And, the decision to skip the briefings may be Fauci’s own, given that he called the sometimes two-hour, marathon events “really draining” recently. Aides also said Fauci is a regular attendee at the closed-door meetings that often take place right before the televised pressers.

Experts agree Fauci’s storied career in the industry means he seeks little praise and doesn’t need the president’s approval to perform his duties.

“If you’re somebody who aspires to have impact in public health as a physician or provider, you should look no further than Dr. Fauci or Dr. Birx, which spans administrations,” said Dr. Vin Gupta, a pulmonologist and global health policy expert who is an NBC News medical contributor. “I think at the end of the day, the president needs Fauci more than Fauci needs any of this.”

His job is considered the “ultimate balancing act,” according to Dr. Kavita Patel, also an NBC News contributor. Watching the president continue to ad-lib medical advice from the White House briefing room “has to be frustrating” for Fauci, whose day job entails research on a potential vaccine, but he is likely aware that the pandemic response will take months and months so he takes a longer view. “He is a runner, and I am sure part of this is viewing COVID-19 task force as a marathon not a sprint,” she said.

Besides the president and Vice President Pence, the only coronavirus task force member who has appeared at more briefings is coordinator Dr. Deborah Birx. Neither doctor attended Friday’s briefing, which was the shortest to date. And, in a first at these kinds of newsers, Trump and Pence took no questions.

White House officials provided no explanation for the abbreviated appearance and lack of medical professionals like Birx and Fauci.

Earlier this month, the president elevated a tweet that contained the hashtag “FireFauci.” Advisers close to both men denied that was ever under consideration and the two later said publicly they had a good relationship and will continue to work together.

Even so, the president does not have the direct authority to dismiss Fauci. The president could, in theory, direct Health and Human Services Secretary Alex Azar to see to it that Fauci is fired. Azar would then have to direct the NIH head to oust Fauci. As a federal employee, Fauci can only be fired “for cause.”

If he were to be removed, however unlikely, it would cause “irreparable harm,” Gupta said.

Occasionally in recent weeks, when Fauci hasn’t been seen among the group of aides emerging from the bright blue doors of the West Wing to start the briefings, observers on social media have wondered aloud: “Where’s Fauci?”

The answer for most of this week, at least: no longer at the president’s side in the daily briefings.