Nancy Messonnier (née Rosenstein; born November 1965) is an American physician who serves as the director of the National Center for Immunization and Respiratory Diseases at the Centers for Disease Control and Prevention. In a February 25 press briefing at the White House, Messonnier warned of the impending community spread of the virus in the United States, stating: "Disruption to everyday life might be severe."[7][8] Following her comments during the February White House press briefing, she did not appear again at the briefing and there was speculation that Messonnier had been "silenced" for her comments stressing the growing urgency of the COVID-19 pandemic in the United States
Messonnier was born in Philadelphia, Pennsylvania, to Robert Rosenstein, who ran a small business, and Gerri Rosenstein, a bookkeeper and local school board president. She grew up in Lower Moreland Township, Pennsylvania, with her brother Rod Rosenstein.
She received her Bachelor of Arts degree from the University of Pennsylvania in 1987. She then attended the University of Chicago School of Medicine, where she received her Doctor of Medicine in 1992. She then returned to the University of Pennsylvania for her residency training in internal medicine between 1992 and 1995.