The new coronavirus could kill millions across the United States, said Dr. Kathleen Neuzil, director of the Center for Vaccine Development at the University of Maryland's School of Medicine.

"It would not surprise me," she told CNBC on Thursday when asked whether the U.S. could see millions of deaths. "We need to prepare for the worst."

Neuzil is the only U.S. member of the World Health Organization's Strategic Advisory Group of Experts on Immunization and previously sat on the Centers for Disease Control's Advisory Committee on Immunization Practices. She's part of the leadership team of infectious disease experts working with NIH to test a coronavirus vaccine and therapies to treat those sick with COVID-19.

"We have 350 million people in the United States, and you do the math," she said on CNBC's "Squawk Box." If 70 million people are eventually infected with this virus and again if there are multiple waves of this virus, then you can do the math and then you can get there."

COVID-19 has now infected more than 9,159 across every state in the U.S., according to Johns Hopkins University, and killed at least 150 people in the country. On March 1, there were about 100 confirmed cases of the rapidly spreading virus in the U.S.