Dr. Anthony Fauci, the leading U.S. expert on infectious diseases, announced Monday that he will leave the federal government in December after more than five decades of service, the AP reported.

Fauci, who is chief medical adviser to U.S. President Joe Biden, was director of the National Institute of Allergy and Infectious Diseases and head of NIAID's immunoregulation laboratory. Even before the coronavirus, he was a leader in the federal response to HIV/AIDS and other infectious diseases.

"I will be leaving these positions in December of this year to pursue the next chapter of my career,” Fauci said in a statement, calling those roles “the honor of a lifetime."

In turn, U.S. President Joe Biden praised Dr. Fauci.

"Whether you’ve met him personally or not, he has touched all Americans’ lives with his work. I extend my deepest thanks for his public service. The United States of America is stronger, more resilient, and healthier because of him," Biden said in a statement.