U.S. President Joe Biden has praised outgoing Chief Medical Advisor Dr. Anthony Fauci for his "unparalleled spirit, energy, and scientific integrity."

Biden's August 22 statement came soon after Fauci had announced that he would be resigning in December "to pursue the next chapter of my career." Fauci said he would be giving up the positions of chief medical advisor and director of the National Institute of Allergy and Infectious Diseases (NIAID). Fauci's statement can be read in its entirety at the NIAID website.

Biden recalled that as Vice President he had worked with Fauci on America's response to the Zika and Ebola viruses.

Biden said he had come to see Fauci "as a dedicated public servant, and a steady hand with wisdom and insight honed over decades at the forefront of some of our most dangerous and challenging public health crises." Biden recalled that as president-elect faced with the ongoing Coronavirus pandemic, he had asked Fauci to serve as his chief medical advisor.

Working under seven Presidents

Biden noted that Fauci had served under seven Presidents from both the Republican and the Democratic Party, starting with Ronald Reagan. Biden concluded his statement about Fauci, which can be seen on the White House website, by saying, "The United States of America is stronger, more resilient, and healthier because of him."

The President echoed those words on Twitter.

'A once-in-a-century public health leader'

Former President Barack Obama tweeted: "I will always be grateful that we had a once-in-a-century public health leader to guide us through a once-in-a-century pandemic." Referring to Fauci's comment about "the next chapter" of his professional life, Obama said: "Few people have touched more lives than Dr Fauci – and I’m glad he’s not done yet."

Vice President Kamala Harris also took to Twitter to praise Fauci as "an incredible public servant whose decades of leadership in science and medicine saved countless lives across the world." She said Fauci had "helped guide our nation through its most challenging public health crises, and I am grateful for his service."

Serving under Trump

In an interview with The New York Times, journalist Sherl Gay Stolberg said that Fauci enjoyed talking to the media and hardly ever rejected a request to make an appearance "except when the Trump White House barred him from accepting them." Stolberg said "In the age of social media," Fauci had not always expressed himself well.

"He uses words like 'multifactorial' that are hard to understand and can be off-putting," she noted

She recalled that Fauci had "never, ever directly criticized" Donald Trump but he had criticized Trump's aides, such as Peter Navarro. Fauci had said that he did have a responsibility to correct inaccurate information given by the President, she recalled.

"I think he felt that it was his duty to do the best he could under the circumstances," Stolberg said.

"It's never really a good time to leave, but you have to leave sometime," Fauci told MSNBC's Rachel Maddow. He said he was interested in lecturing or writing. He also said he wanted "to encourage young people to go into public service."

Fauci told Maddow that a big lesson from the COVID pandemic had been to "never, ever underestimate an emerging infection in which you don't know where it's going because we've been fooled before."

Fauci said the number of infectious diseases was increasing. He added: "About 70 to 75 percent of all the new emerging infectious diseases are zoonotic, namely they jump from an animal species to a human."