U.S. top infectious disease expert Anthony Fauci announced Monday he plans to step down from his roles at the end of the year after more than 50 years of public service.

Fauci serves as U.S. President Joe Biden's top medical adviser and the director of the U.S. National Institute of Allergy and Infectious Diseases (NIAID).

"After more than 50 years of government service, I plan to pursue the next phase of my career while I still have so much energy and passion for my field," Fauci said in a statement.

"I want to use what I have learned as NIAID Director to continue to advance science and public health and to inspire and mentor the next generation of scientific leaders as they help prepare the world to face future infectious disease threats," he said.